score:5
The answer will need to be broken down into four parts as you'll be dealing with multiple jurisdictions on this trip.
Currently the US does not place any restrictions on passengers entering the US by air, only the land borders with Canada are closed. Hence immigration should allow you to enter with a valid US visa.
The local government asks tourists to get tested 72 hours or sooner before traveling and to get another test on arrival if you're staying for more than 3 days. So if you can get a test in Toronto before traveling, you're good to go.
The state doesn't seem to require quarantine for international travelers (unlike New York) and the District of Columbia is one the list of territories exempted from travel restrictions. So you should be able to enter without being required to undergo a 14-day quarantine.
Anyone coming to Canada (except for truck drivers and essential workers) is currently required to undergo a 14-day quarantine at home, so you should plan to spend 14 days in isolation when you return.
Overall I can recommend either staying in Toronto or amending your plans to visit a state without travel restrictions, such as Florida, Texas or Arizona. Remember to wear a high-quality mask (KN-95 or N-95) everywhere and avoid maskless indoor settings such as restaurants and bars.
Upvote:-1
Also it does not state anything specific for travelers with less than 14 day stay in the US.
The quarantine (which I don't think apply to you) doesn't prevent you from going to the airport.
Update: no idea why this answer got downvoted. JonathanReez's answer points to https://washington.org/dc-information/coronavirus-travel-update-washington-dc, which confirms my answer: can go to the airport (and no quarantine). Also, no need for COVID test if staying less than 24 hours in DC.