when did Christians in America become infatuated with Zionism?

Zionism ceased to be when the nation of Israel was born. Have the guts to deal with the facts. 

American Christianity never had the level of antisemitism nor bigotry of Europe or the Middle East, ESPECIALLY after the Holocaust! Now most of that bigotry is gone leaving simply recognition that Christianity grew out of Judaism. American Christians simply have a cordial, friendly relationship with Jews and of their shared Judeo-Christian traditions and values they share.

Because of Romans 2:28-29, Philippians 3:3, and Galatians 6:16.  Unavoidable.

study the Religious Right of the 1930s.

It has nothing to do with America.  It has everything to do with the New Testament, which makes it clear that the land of Israel belongs only to the Jewish people, and which makes it clear that the Jewish people are brought back to Israel in the last days, and which makes it clear that Christians are to love, bless, protect, and defend Israel and the Jewish people.  So shut your boring piehole, because you have no life.

God told me my vision it was a sign to Egypt and Israel so I believe him. Just showing you that the mosaic Covenant is broken except for the curses God will still do that good thing to Judah Jeremiah and a remenat Isaiah 28 believe in the corner Stone if mosaic covenant isn't broken why do you need Jeremiah31 new covenant where God will remember your sins no more. That said does God remember the sins of the mosaic covenant Isaiah 2 says yes