I'm not sure friendly is a word I would use to describe Iran, and Saudi Arabia would exist with or without American support. The US-Saudi alliance is rocky at best, and only exists because the Saudis have oil, and largely persists because Saudi hates Iran, which is important to the US because of their strong alliance to Israel. You have to choose sides in the Middle East, and the US chose Israel. Everything else flows from there.

The US is an enabler of Saudi nonsense, but the Saudi state is not being propped up with American resources. They would be powerful in the region regardless of American support.