I don't agree with everything in this letter--it's a little too sweeping for me. But the core of it, that there are things, having grown up here, that you see which people who come from other countries miss, really struck me:
Your obvious shock and dismay at the sheer angry ignorance of the health care teabaggers reiterates my largest problem with your rosy immigrant's view of America. You have often underestimated just how poisonously dangerous the American populist right is.
I don't blame you. You came to America after the rise of Reagan. Most of your life in America, you have lived under different Republican presidents who placated these folks with platitudes and campaign rhetoric. The one period when the populist right didn't feel they had a fellow traveler in charge was when Bill Clinton was elected (thanks to the reactionaries splitting their votes). You remember, no doubt, the level of crazy Clinton had to defuse and dodge, and this was a man who had the advantage of being a Southern bubba who has dealt which such people all his life.
For most of your time in America, this insanity has been muted by the success of conservative politics. Since you live in Washington, you probably saw daily the face of the successful conservative political establishment that milked the populist right, and by milking them kept their bitterness at a manageable level. That safety valve was stuffed up by George Bush's failed presidency.
So now, these people are facing their worst fears; actual change. A political and demographic re-alignment is happening before their eyes, and they are reaching back into their old bag of tricks of intimidation, violence, and apocalyptic fearmongering. You are British, Andrew. You love this country, and we love you for it. But you didn't grow up around these folks, and you don't realize what a permanent and potent part of the American political landscape they are.
It's worth reading the whole thing. I've often wondered how much of Andrew's conservatism, and really the politics of the "serious" left (TNR, Slate, Washington Monthly, a chunk of the Atlantic) is rooted in an utter disdain for the late 60s--the riots, free love, the drugs the Panthers etc. It's understandable, but obviously very weird for me. Anyway, read the whole thing