And how does it relate to the growing number of judaic people migrating there even prior to Word War II?
The United States did not set up Israel. If anyone did, it was Britain (who had ruled the land under the League of Nations mandate system since WWI), or the United Nations (who proposed a partition of the Mandate between Jewish and Arab states in 1947), or popular pressure from the growing Jewish population who mostly supported the Zionist movement for an independent Jewish state.
Here's a good previous thread that goes into more detail, especially the top answer from /u/tayaravaknin.