Biden says the U.S. would have to invent an Israel if it didn't exist. Why?

Same reason they invented Israel IRL: So nations around the world can turn away boatloads of Jewish refugees in the event of another genocide and so "the international community" can have a pro-West power in the Middle East.

https://embassies.gov.il/washington/Obama_in_Israel/Pages/The-Ultimate-Ally.aspx