Christianity as it's practiced in the USA is a very weird and disturbing mix of fundamentalist religion and politics.
Perhaps that is so, but your further statements weaken your argument by showing your own bias.
After all, you can go into any typical American "evangelical Christian" (aka fundamentalist) church
Repeat after me: evangelism != fundamentalism. There are evangelicals who are not fundamental. And there are fundies who aren't particular evangelical. Evangelism is the process of spreading what you believe. Fundamentalists share a certain set of beliefs. They are not mutually requisite characteristics; neither are they mutually exclusive.
Specifically, I am an evangelical preacher who is decidedly not fundamental. My churches (two) are, I imagine, reasonably typical American evangelical Christian churches.
and they'll preach about how the USA needs to wage wars in various countries,
I have never preached the need to wage war, for or against anything. Period.
how you (the congregation) needs to vote for these particular politicians,
Any preacher, of any stripe, who does this in the US risks losing his church's 501(c)3 status. The IRS takes a dim view of PACs pretending to be churches.
how we need to worship The Invisible Hand, how rich people are better people than the rest of us because God has blessed them with so much money and "success", etc.
For an excellent example of a fundementalist evangelical mega-church pastor who specifically denounces these ideas, read "Radical" by David Platt..
Now obviously, not all Christians in America believe this crap, but the numbers of fundies has actually outgrown the number of "mainstream" Protestants in the USA,
Citation, please. Here, I'll loan you one. According to [something I just found on the Internet], of the five largest denominations in North America, only one, the Southern Baptist Convention, fits your stereotype. The fastest-growing denominations are LDS, Assemblies of God, the Roman Catholic church, and the Orthodox Church in America. None of these fit your image, either.
and they are a very strong political force (esp. since they are so politically involved, unlike most other religions).
The question isn't how politically involved the churches are as corporate entities. The question is how politically involved are the members. The most recent POTUS have been (in reverse order): UCC, UMC, SBC, Episcopalian, PCUSA, SBC, and Quaker. Only SBC comes close to fitting your stereotype, and I doubt you'd describe Bill Clinton or Jimmy Carter as the war-mongering money-loving elitists that so upset you.
Please: 1) don't confuse evangelism with TV-broadcasting, money-loving, success-preaching fundamental evangelicals. 2) Don't believe that fundies control the US religious landscape any more than you should believe that FOX news controls the political landscape, and 3) Don't believe everything you see on TV about Americans, or Christians.
I bid you peace.