Get an old Encyclopedia Britannica, maybe before 1985. Then get an even older one say 1920. Study everything you can find about Americans and American History. In my experience the British of that era give a much more accurate account of America.
Of course you will need something else for modern history.
I know you want online but there is no reason you can’t read those old encyclopedias plus a lot of people will give them away or sell low.
Back in the 70’s my folks had an Encyclopedia set from the 30’s. I had to do a report on the moon. So I went to the trusty M volume and learned that the moon just MIGHT be made of green cheese!
Mom took me to the library to find a bit more updated sources.
The 1911 one is the best.