1. Why is the bad guy in American films always an Englishman?
Well, that's self explanatory isn't it? After the unpleasantness of the 1700s, you don't expect us to trust you, do you?
2. Why do the Americans invariably end up assasinating their Presidents. (in that they either actually shoot them or impeach them for having blow-jobs in the White house)
A bit of exaggeration there. Of the 18 presidents since 1901, JFK was the only one killed. Nixon resigned after trying to cover up Watergate. Reagan was shot by a psycho. Clinton's problem wasn't that he got caught with his pants down, it was that he lied about it under oath -- if he hadn't lied, he wouldn't have been impeached.
OFBSLF