Thanks for the interest.

I'll try to go top to bottom here, and then you let me know whenever I hit something that you really want to know more about, &c &c.

Due to [insert obscure, distant-past history that might bore anyone but myself], Judaism spread in Magical Europe in a way that it didn't among the muggles. Meanwhile, Christianity in general couldn't take off how it did among the muggles, so the religious landscape is rather different in the Magical world.

(Where it exists at all, mind. Wizarding Britain has been incredibly secular for a long time now.)

British Wizards have stronger ties to the Welsh (the original inhabitants of England) than to Anglo-Saxon culture. Given present prejudice against muggles and the mixing of bloodlines, there are few wizards who care that much, but this still survives in some of cultural traditions. And you can still find some wizards who twist "Anglo-Saxons overran the Welsh" into a tale illustrating the dangers of muggles overrunning wizardkind, even though Welsh wizardom was actually able to weather it pretty well.

Also interesting but not incredibly relevant, so I'll skip them unless you're interested:

• Why the Ministry of Magic is called a "ministry" despite ostensibly not run as an arm of the Muggle government.

• The Ministry of Magic also controls much more land (with regard to the local magical populations) than the United Kingdom does today.

Skipping ahead some we come to the colonization of North America. First off, magic is weird here. Not a wasteland or anything, but you almost need to use magic differently, as if you have to zig where your training makes you want to zag instead. Besides the readjustment period (and temporary nausea for sensitive people), the other major effect is that muggleborns are not very common. Intermarriage produces wizards just fine like in the Old Country, but it's rare for new bloodlines to arise. This means that the countries over here have smaller populations than normal, but also that those magical populations can manage to be even more insular than, say, Wizarding Britain.

British wizards settled North America to get away from the Ministry and run with a much longer leash. Eventually they rebelled (and thank goodness, because the fledgling United States had a ridiculous number of lucky breaks that they couldn't have done without) because, um, they wanted a king.

(There is a long history here of wizards contributing to or even starting muggle conflicts for reasons of their own that really have nothing to do with what the muggles are fighting over. Grindelwald and Hitler may have supported each other but they had entirely different goals, and when Wizarding Britain fought Grindelwald it was to oppose Grindelwald's aims; they didn't really think much of Hitler except as an ally of Grindelwald).

As far as the Wizarding World was concerned, the important thing that happened after the American Revolution was the founding of the Kingdom of Fourteen (K14).

The present political situation is illustrated by this very badly-done map: (map)[http://s1175.photobucket.com/user/Ryan_Gauvreau/media/us-states_zps0bce392b.gif.html?filters[user]=140536670&filters[recent]=1&sort=1&o=0]

The Constitutional Federation of the Art broke away from the K14 in a revolution of its own; "Art" refers specifically to legilimency, which the CFA plays around with in potentially worrying ways. The Independent Territories are a collection of small states. Free Wyoming survives by virtue of playing everyone against each other, as nobody is willing to split the pie with anybody else. The Aztecah go down through Mexico, and a tradition that survived the Spanish Conquest. Hawaii isn't owned by any of these powers, and it's far enough away that nobody thinks this is unusual.

Borders as you seem them on the map are not exact (the K14 has some of Canada, for instance) but they should give a general idea of how things are.

Hopefully this was all neat and not of it was boring and apparently unnecessary. I have spent way too long thinking about ancestral migrations and cultural exchanges through wars and crap like that (I mean, the whole Judaism thing goes back almost two thousand years). o.0