In my field (Medieval Lit), there seems to be as much American scholarship as there is British. Some of the basic analyses and theories are British while lots of critical/postmodern theory is American. My MA thesis supervisor in York was American and I met quite a number of American scholars at Conferences in England and on the continent.
I'm originally from Germany, currently living in London, and I have a German Magister Aritum from Cologne as well as a British MA from York. In 2010, I was accepted into the Queen's Belfast PhD programme but had to quit due to decreased funding and the decision by the School of English to turn their backs on Medieval Lit in favour of Renaissance and Contemporary Lit. Now I'm trying my luck with some US schools, my top choice being Notre Dame's Medieval programme.