Once upon a time - in 1946, to be more precise - American Christian support for Zionism was expressed through an organization called the American Christian Palestine Committee. Its membership was drawn principally from liberal churches, and in the run-up to the establishment of Israel it played an important role. Some years later (1967), Dr. Franklin Littell founded "Christians Concerned for Israel," again drawing mostly on mainline churches, and in 1978 CCI grew into the National Christian Leadership Conference for Israel.
So "Christian Zionism" has roots in this country.