I'd say that most Welsh and Scottish people do not associate themselves closely with "Britain" the word as they were once not part of it- it has always been seem as a colonialist term, taking independence away from Scotland and Wales. England may have been responsible for the creation of Britain, but most Brits dont self-relate to themselves as British, preferring Scottish, Welsh or English.
Americans I assume love their country and wish to remain American. Scots in particular seek to be Scottish and viewed as such. They vote regularly (and separately from England) on issues of gaining greater independence. They have their own indigenous language, as do the Welsh, few parts of America, bar Hawaii could say this- except indigenous tribes spread thinly. Its a nationalistic pride thing for many. I'm Northern Irish, part of the UK, but not part of Britain- I have an Irish accent, but because I can see Scotland from the coast of Ireland on a sunny day, some English people assume I'm Scottish. I know what you say Owen about how close and localised it can go, but its a major political issue in the UK. It just grates on Brits to hear "British accent" as we hear it chiefly come from US TV and we (rightly or wrongly) assume people to have no real knowledge of "British" culture or people. No offence intended throughout, if we didnt all sound different, how could we fill all the NPCs in Dragon Age, Elder Scrolls and tons of others? Yay for accents.
