No, America's favorite sports are played by people the world over. There's a Nigerian, New Zealander and a Dutchman on the Minnesota Vikings, in the NBA, there are Russians, Liberians and even Chineese. In baseball, there are Cubans, Mexicans, Japaneese, Koreans, Aussies, and even Russians and Itallians, and in hockey.. well, it's possibly the second most internationalized sport.
Seems when Brits say nobody else plays our sports, it's usually because no Brit could ever cut it in any of our sports. 'Cept for Owen Nolan, and he grew up in Canada.
Actually, I forgot that Owen Nolan is from Ireland, not the UK. You're screwed there.
BTW, how many soccer players in the P-leauges are American? Point, set match.