Social democracy =!= socialism. The take over of failing private enterprise by the state is in no way comparable to a from below revolution that establishes worker's control of the means of production.Britain nationalized a lot of its own economy in the aftermath of the war and I don't recall the U.S. complaining at all.
http://en.wikipedia.org/wiki/Social_democracy
Based on the list, one could argue Britain was a social democracy between Chuchill and Thatcher.