I've noticed that "Santa" is really starting to displace "Father Christmas" in British English. When I was a kid if you said "Santa" you'd have been scolded for using the American name, but listening to kids now I hear them say "Santa" all the time. I blame TV.
"Crosswalk" sounds extremely American to me and I've never heard anyone say it in Britain, but maybe I'm just getting old.
That’s a fair example, I think I’ve always seen Santa and Father Christmas as interchangeable and wouldn’t necessarily associate one of them with being the American one. A hypothesis I’d be curious about - I wonder if there’s a correlation between how commercialised something is and how Americanised it becomes. In that case I guess we won’t be calling them crosswalks any time soon.
The modern folklore (comes down the chimney, rides reindeer etc) is an American invention that came to Britain in the 19th Century. “Father Christmas” was an older British folk figure who got merged into the American tradition.
"Crosswalk" sounds extremely American to me and I've never heard anyone say it in Britain, but maybe I'm just getting old.