Can an American join the R.A.F.?

I'm 21 and a US citizen. I've been planning to join the USAF for quite some time now but to be honest I'd rather join the R.A.F.. For starters, the US military is strong enough whereas Great Britain is a much smaller country with a greater need for a stronger military. I would much rather serve and defend Britain than my own country, as bad as that sounds. After all, it is where my family came from in the 1600's and everything about the country has been much more appealing, whether it be it's history, the way it's governed, the people, lots of things. Basically the gist of everything is that I'd rather join the RAF than the USAF, can I?