The Christian right, which although maybe isn't a majority of Americans is a significant fraction, unconditionally supports Israel for a number of reasons, from Israel being necessary for the Rapture to it being better than its neighbors, to simply being anti-Muslim.

See http://www.patrobertson.com/Speeches/IsraelLauder.asp for their own words, and http://www.lewrockwell.com/orig/north7.html for an non-evangelical viewpoint.