The curriculum in UK schools is structured quite a bit differently from US schools, so you would have to make sure that you are comfortable with that.
One place to start is with the Russell Group, a loose affiliation of 24 highly regarded research universities in the UK. As pointed out above, many uni websites have explicit information for international applicants. If you are serious, there is no substitute for visiting beforehand.
Some other options to consider: Germany now has some fully English language undergrad programs for Americans. There is also a unique 2+2 program between William & Mary and St Andrews–you spend 2 years at each and get a joint degree. Also, many American universities will let you do a sophomore or junior year abroad. Arcadia Univ near Philly coordinates a lot of international programs.
Speaking from experience (Australia), there is a significant learning curve to being a US student enrolled in an overseas uni (as opposed to being a study abroad student). It is very rewarding, but do a lot of research so you know what you are getting into.