i don't even see how there could be a movie defined as "british" or "american" anymore. Half the time the director is either british or american and the cast is the opposite of that or half is american and half is british. Just because a movie takes place in England or just Europe does not mean it is a "british" movie and just because it takes place in "america" does not mean its an american movie. .
if you think american movies are just "american pie" and "clueless" and you think british movies are just "spiceworld" and "chicken run" than... i don't even know where you are coming from... i think they are pretty much equal when it comes to producing amazing movies as well as awful movies.