There are teams for basically anything in big cities. But if you stop a person in the street and ask them the rules for baseball, they will probably scratch their head and come up with something like "Erm... They use a bat, right?"
At schools, children mainly play football (what Americans call "soccer"), basketball or volleyball.
Yes, but I doubt there are any Americans who haven't played baseball, unless they were disabled as a child.
I don't care for baseball but played it on both the east and west coasts growing up because I had to in school and our neighborhood and church(on both coasts) played baseball together.