The problems seem to come from the roots of modern US evangelism. The 19th and 20th revivalist movements that formed the basis of the US evangelical church was the product of a settled agrarian society, and so was socially inclined to extreme conservatism as a result of its roots. The great wide spaces of the prairie spawned the Bible Belt and the roots of the Christian Right.
Meanwhile in Europe, the great revival movements came out of the heart of the industrial and agricultural revolutions, and produced many of the minds that formed the basis of the Labour movement (take for example the role of the young Methodist Church in the story of the Tolpuddle Martyrs). Elsewhere, evangelical churches have been spurred by social injustice in all its forms - in South Africa, across South America, and in the former Eastern Bloc.
And so there is a fundamental (ahem) difference in our fundamentalists...
[See the comments for a correction from pnh. I think I need to read some more US history before pontificating again!]