It's called selfishness... The US can be powerful, but China can't... The US can havee the power to destroy the entire planet, but if another country has a single nuke, they're evil... The US can have the world's biggest economy, but if another country creeps up, watch out! The US did it with "democracy", and the Chinese did it with "communism" (the quotation marks are there because the US isn't a true democracy, and China isn't a true communist regime...).

The bottom line is that the US hasn't had any competition for some years now, and I think it's high time that another country challenge American supremacy, cause the US is really starting to piss everybody off big time.