Europeans are so good at the American accent! Not so much us accept Meryl....she can do anyone. I 'm sure there are others but the worst ever Brit accent by an American actor was Kevin Costner in Robin Hood MHO.....I liked the movie kind of but he was a big weak link accent wise. The best actor in that was the bad guy..... Alan Rickman..... so sad he died too young. That was the first movie I noticed him in.
one of my laugh out load bits from that...probably won't translate without seeing how over the top and funny his bad guy was but what the heck
the "cut your heart out with a spoon" bit
https://www.youtube.com/watch?v=MhfuuKiTcYQ