Why did the dominance of maize last so long in North America?

This is a really complicated question. I will try to be brief. In order to discuss corn its relevant to discuss other major crops. The reason is that farmers choose to grow things that will compliment another thing to prevent soil erosion and lower costs.

In North America, fields are often planted in a two-crop rotation with a nitrogen-fixing crop, often alfalfa in cooler climates and soybeans in regions with longer summers. Sometimes a third crop, winter wheat, is added to the rotation.

Corn and potatoes are the native "grains" to the United States. Peanuts (in the Southern US), alfalfa or hay have traditionally been used in crop rotations. Turkeys, deer and bison in the Great Plains were the major native protein source. Bison were intentionally killed off as a genocidal measure against the Plains Indians, but we continue to eat turkey. There were no native domesticated farm animals or beasts of burden in North America, so settlers brought these over, such as horses, oxen, cows, and hogs. Wheat, oats, barley and since the 1950's soybeans have been farmed extensively as well, which were brought over too.

Farm animals, like horses, cows and oxen do not eat corn. (Today now we have our ways of making them eat it by processing it...) So, corn is an excellent crop for small farmers that do not keep large, expensive farm animals, but rather keep only hogs, turkeys or chickens. The farmer doesn't have to grow too many crops to feed himself and his animals with the system. In early America most farmers were yeomen farmers. In the Southeast, this model was very popular.

Corn as far as I can tell does grow most places in the US with suitable farm land, even in the Southwest. I don't think its soil issue, although it might be, (see below "Dust Bowl") as much as a climate issue. Europe is colder than most of the US. Since wheat requires a colder climate, it was grown in the Northeast and then extended into the Midwest where it was found to grow very well.

There are some historical reasons why wheat was not popular early on. Although the Northeast grew wheat, oats and barley farming was not extensive since the land suffered from soil erosion quickly and it was not profitable. The reason given is farming practices using oxen, which were non-native, and deep plows used up the the land too quickly. Also, in early America there was not yet railroads to move the wheat to market, so people ate what was local.

Midwest Wheat was first grown in large amounts in the Midwest in the mid 19th century, because there were agricultural markets, a suitable cold environment, and it was useful in crop rotation with corn.
Another possible reason the Midwest starting growing wheat is that large amounts of German immigration meant that it had a unique culture. In Germany wheat is the major crop so that's what they grew. German immigrants were also instrumental in altering American beer. If you want to read about corn beer, see this

As the Midwest opened up to settlement via waterways and rail in the mid 1800s, Germans began to settle there in large numbers. The largest flow of German immigration to America occurred between 1820 and World War I, during which time nearly six million Germans immigrated to the United States. From 1840 to 1880, they were the largest group of immigrants

In the Midwest, corn is still the major crop by far and always was. Its actually known as the "Corn Belt." Wheat is today only grown west of the Missouri River.

Still, until the 20th century the majority of Americans ate their local foods. A few important changes occurred after the Civil War: The US Homestead Act continued to offered farm land in the "Heartlands"

The US government encouraged farmers to grow wheat to meet international demand created by WWI

During WWI, Europeans could not grow enough food because they were fighting and they eat wheat. The price for wheat thus rose dramatically. The US at this time also started international food aid programs, supplying food to Russia during its famine for example.

The above policies caused the Dust Bowl, so during the Great Depression following WWI, Roosevelt reorganized American agricultural practices

Many of the lands opened to settlement and farming were unsuitable and marginal farm land. An ecological disaster occurred in the middle states of the US due to extreme soil erosion and drought called the Dust Bowl. Farming practices were changed favoring larger, more concentrated farms. Share cropping, which was still very common in the South, was also discouraged through the social security system. The effect is many fewer people were engaged in farming. By WWII, the US began mechanizing most of its farming operations and even fewer people were needed. This meant that they were buying food instead of growing it.

In the early 20th century, breakfast cereal became popular. It was first introduced as a treatment for insanity and mastrubation, but the market became very competitive very quickly, with 40 companies being founding in the early 1900s. Cereals were offered made from corn, wheat, bran, oats, of all different varieties. Americans began to eat packaged food with increasing frequency. With a national market, Americans could choose what to eat. Over time, Americans started to choose to eat wheat along with corn in their diet. Much of the corn grown today is either shipped internationally, used as animal feed by flavoring it or turned into corn syrup, corn oil or other corn-based food products. Soybeans, another Old World crop, figure prominently in most American packaged foods.