Basketball
Technically no. The Olympics are for "amateur" atheletes, those who do not make their livelyhood by the sport they compete in.
All of them.
Baseball
wrestling
Swimming.
Karate is not an Olympic sport.
The only sport the US does not compete in at any Summer Olympics (including 2008 and the upcoming 2012) is handball.
We have the Olympics so that athletes from all the world can come to compete in the sport they love (and hopefully win a medal:)
none, we play Cricket as our national sport, but I don't think we compete in the Olympics.
England is poor at sport
every single event from tennis to skiing
There are a lot of countries that compete in the wrestling Olympics the bigger countries in the sport are Russia the United States