> Iran would be of no concern to the US if not for Israel.

This is only true if you completely ignore the Sunni Shia split and our relationship with literally every other country in the Middle East excluding Israel.

Edit: This is evidenced by the fact that when Iran was attacked by The US and Israel, they bombed a bunch of neighboring countries with US bases. None of those countries have alliances with Israel. (Although they are certainly less hostile than other countries in the region)