As for Pakistan, which isn’t even in the Middle East:
That depends on your definition of the Middle East. Pakistan is sometimes included.
I’m not sure the US is or should be concerned with the Middle East uniting, all you have to do is look at all of recorded history in the middle east to see that’s not realistic.
What? The middle East has been united for most of its history since the Rashidun Caliphate. It was also reasonably united against the US in the 70s, causing the oil crisis. United doesn't have to mean one country.
“Hey we’re not happy with what your PM is doing and if it continues don’t expect support from us.” Is somehow the US doing regime change?
I mean look at Cuba and none other than Iran itself. "Don't expect support from us" is putting it lightly; we've what the US does to governments it doesn't like. The US put pressure on the Pakistani military to remove the democratically elected PM and install one friendly to US interests, that's two steps removed from a coup.