Which places in the USA have been ruled by all three colonial powers, British, French, and Spanish?

If you are willing to accept some other colonial powers, we can expand the candidates with Fort Ross. Originally inhabited by the Kashaya Pomo people, Russian adventurers established a settlement on Bodega Bay in 1812. By 1841, the colony had declined in relevance and was sold to a Mexican citizen of Swiss descent. It then became part of the United States along with the rest of California as part of the peace treaty with Mexico after they got "skunked" by the USA.

West Florida

Source: Wikimedia Commons CC-By-SA 4.0

The area along the Gulf Coast from the Mississippi River eastward was settled by the French and Spanish. The French settlement in this area was all part of Louisiana. These were all French settlements:

• Natchez
• Baton Rouge
• Biloxi
• Mobile (the original capital of Louisiana)

The Spanish settlements were all part of Florida. The main Spanish settlement here was Pensacola, but the French captured that in 1719 during the War of the Quadruple Alliance.

In 1763, after the 7 Years' War/French and Indian War, the French ceded Louisiana (west of the Mississippi, including New Orleans) to the Spanish. But the coastal territory east of the Mississippi was ceded to the British, along with Florida proper.

The British divided Florida into East and West Florida at the Apalachicola River.

In the 1783 Treaty of Paris ending the Revolutionary War, the British gave all of Florida, including West Florida, back to the Spanish. The USA and Spain never really did agree on the northern border of West Florida.

Now weird stuff happens.

"His Catholic Majesty promises and engages on his part to cede to the French Republic six months after the full and entire execution of the conditions and Stipulations herein relative to his Royal Highness the Duke of Parma, the Colony or Province of Louisiana with the Same extent that it now has in the hand of Spain, & that it had when France possessed it; and Such as it Should be after the Treaties subsequently entered into between Spain and other States."

Napoleon was able to strongarm the Spanish King, via the secret Treaty of San Ildefonso, into giving Louisiana back to the French, who promptly sold it to the USA.

But the status of West Florida was ambiguous: Was it Louisiana or was it Florida? It was a power vacuum because all of the armies were engaged in Europe.

The Louisiana Purchase Treaty directly quotes the Treaty of San Ildefonso with the above text. The sticking point was defining what extent Louisiana "had when France possessed it".

In the meantime, American settlers had been moving into the area, with their slaves. In 1810 they declared independence and set up a short-lived Republic of West Florida.

President James Madison declared that West Florida was part of the Louisiana Purchase, and since the European powers were busy, nobody stopped him from sending US forces to occupy this strip. West Florida was officially ceded by Spain in 1819 , along with the rest of Florida.

You've probably answered your own question your way satisfactorily. However, it got me thinking about the beginning of exact dialogue in question. In fact, I think you've found something new here about the Charles Addams' Addams Family that I haven't seen anyone else mention before.

“That new one,” he said. “You know, the one that took over after my government, Los Conquistadores, got skunked.”

“Oh, yes, the United States!” said Morticia.

Unlike her later statement (which was arguably a generalized one, meant to apply across the board geographicaly), this bit is inarguably directed at the specific locale Fester is talking about.

So what we are looking for here is somewhere conquered by a country for whom the phrase "Los Conquistadores" makes sense, and then the United Stated "skunked" them and took it. "Los Conquistadores" is Spanish, not French or English (and of course the "Conquistadores" were generally considered to be Spanish). "skunked" implies there was some kind of competition, almost certainly a war, which one of the sides lost badly.

The only war directly between the USA and Spain where Spain lost badly and was forced to give up territory was the Spanish American War.

One could perhaps stretch things a little, and consider the leadership of the Mexican Republic the inheritors of the Conquistadores, particularly if you are one of the people in that culture who consider White Mexicans to have historically been the elite ruling class of the country¹. If you do this, then the Mexican-American war would also be a great candidate.

So now the question devolves to territories the USA took from Spain after the Spanish-American war, or alternately perhaps took from Mexico after the Mexican-American war.

From Spain:

The United States gained Spain's colonies of the Philippines, Guam and Puerto Rico in the treaty, and Cuba became a U.S. protectorate.

From Mexico:

The USA acquired the disputed portion of Texas up to the Rio Grande, plus California, Nevada, Arizona, Utah, and parts of what are now some neighboring states.

One could also stretch it a bit further to include the Texas Revolution, on the theory that the newly independent victor petitioned to join the USA almost immediately.

In this case, what was acquired was the core of the modern state of Texas, plus an arguable claim on much more territory that proved quite useful to the US in starting the Mexican-American war.

The sensible thing at this point is to dive back into the show lore to help us narrow it down some. This is where things really get interesting. Prior to the 1960's show, the characters didn't have a cultural heritage, or even first names. In the 1964 episode "Art and the Addams Family", Gomez was revealed to be Spanish. However, in that same series, Fester was related to Morticia rather than Gomez (unlike the 80's movie and Netflix universes). We don't have any further information on Morticia's background from the 60's TV show²

This was all I was able to find researching online. However,this quote in the question in fact gives us more information, which I think is a real find. It implies the answer to this question also further nails down the cultural identity of Fester, and presumably also that of his niece (in the 1960's live action universe) Morticia. Further, the strongest implication here is that that heritage is Spanish (with Mexican being an alternate possibility).

The implication of all this is that, in the original TV lore at least, the Addams Family is technically Hispanic on both sides of the family.

^{1 - I'm taking no position on this matter myself. I have my suspicions, but the research I did shows that the matter is under dispute, and I'm not conversant enough with the culture to confidently take sides in writing. However, this is the position that some people have, and Fester could well be one of those people.}

^{2 - She does often speak French, but not well enough for it to be her first language}

Here are the results of my own research on the subject of areas of the USA which were colonized by the three major North American colonial powers.

Various groups of Amerindians (Indians or Native Americas) once ruled or at least lived in every single place in the USA.

As far as I know even Aztec legends never indicated their ancestors ever lived north of the Rio Grande, so I am ignoring the Aztecs.

In 1873 General Crook's proclamation of victory over the Tontos said that his troops had ended a war which had been going on since the time of Cortez, apparently implying a connection between the Aztecs and the Apaches. If an official document could exaggerate that much, Morticia could exaggerate equally much in an offhand statement, and I don't think we need accept a period of Aztec rule.

Great Britain ruled the 13 original colonies along the Atlantic coast and also granted to the new USA in 1783 the lands east of the Mississippi River and south of the Great Lakes it had acquired from France in 1763. Great Britain ruled Florida (including southern Alabama & Mississippi) from 1763-1783.

West of the Mississippi Great Britain ruled or claimed parts of Minnesota & North Dakota until ceding them to the USA in 1818. Great Britain and the USA shared rule of the Oregon country from 1818 to 1846, when Great Britain got the northern part and the USA got Washington, Oregon, Idaho, and parts of Montana and Wyoming.

France claimed the Mississippi River basin, or about half of the lower 48 states, though their forts and settlements were thinly spread. The part east of the Mississippi were ceded to Great Britain in 1763 and became part of the USA in 1783. The part west of the Mississippi was ceded to Spain in 1763, back to France in 1800, and then to the USA in 1803.

Spain originally claimed to rule all of the Americas west of eastern Brazil.

A Small French colony was established at Charles Fort on Parris Island, South Carolina in 1562 which was abandoned in 1563. A second French settlement there lasted from 1577-1578. The Spanish settlement of Santa Elena on the same site was occupied from 1566 to 1576 and from 1577-1587, the region was later ruled by Britain for about a century before the American Revolution.

But Gomez implied that the USA acquired the region they lived in from the Spanish government.

In 1819 a border treaty caused Spain to cede a small part of Colorado to the USA; there were probably never any Spanish, French, or British settlements or forts in that area. Spain also ceded the western part of the state of Louisiana, which probably had a few French and Spanish settlements and forts. I don't think that the British ever had settlements in that part of Louisiana.

Spain ceded East Florida to the USA in 1819. A French settlement was at Fort Caroline in modern Jacksonville from 1864 to 1565. The Spanish established Saint Augustine in 1565. And East Florida was ruled by Spain from 1565 to 1763, by Britain from 1763 to 1783, and then by Spain until 1819.

Spain also ceded West Florida to the USA in 1819 (which had been occupied by the USA since 1812), a region including the southern parts of Alabama and Mississippi and eastern Louisiana. The French established Mobile, Alabama in 1702 and Biloxi, Mississippi in 1720. The region was ruled by Great Britain 1763-1783 and then by Spain until the USA acquired it.

Natchez, Mississippi was founded by the French in 1719. The region was ceded to Britain in 1763. During the American Revolution, the Spanish captured the region in 1779. It was ceded by Britain to the USA in 1783, but Spain retained it until a US military expedition claimed it in 1797.

I am rather surprised that there are any regions in the USA which have been ruled by Spain, France, and Britain, and I suspect that Jack Sharkey would have been equally surprised to learn that there were places which had been ruled by everyone he mentioned (except the Aztecs).

Most of those regions were were ruled or settled or claim by Britain much longer than by France or Spain (South Carolina) or by Spain much longer than by Britain or France (East Florida), or by France much longer than by Spain or Britain (Alabama & Mississippi).

And I would certainly be pleased if someone pointed out a region where the three colonial powers ruled for time spans closer to being equal.