I can't point you at research but I've recently found that it does seems like my American friends have a much tougher time understanding British-English than I

I can't point you at research but I've recently found that it does seems like my American friends have a much tougher time understanding British-English than I do as a non-native English speaker and from my experience non-native speakers don't care what version is used as long as it's consistent (for those that care a little at all). Personally I don't really notice if I'm reading American or British English, I only notice when it's pronounced. I too would love to see research.