I think that Israel would be really cool. It's got all those historic places, and the culture would be way different. I wouldn't want to go to Brasil or China. I know people who live in Brasil, and they're description doesn't sound that impressive. I have friends who went to China this summer. They had a blast, but it didn't sound that great to me.
Where in America would you go? I live there, so I can't say I would want to go there if I had a choice between here and Israel, but if you said where specifically in America, I would be able to help you out.