A crude search of the COCA and the BNC shows that it is we is just over nine times more frequent in American English than it is us, but only about five and a half times more frequent in British English. There may thus be a certain amount of instability in the use of the first person plural personal pronoun, as indeed there is in all personal ... More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.