"Withdrawing" to 1990 borders? You mean expelling the states that joined after 1990? I'm not sure that would go over well with the Baltics, Romania, Sweden and Finland. Withdrawal from NATO is voluntary and cannot be compelled.
NATO in its former shape has pretty much been dismantled over the course of last month.
[1] NATO minus the US is still alive, of course.
I'd also find it hard to imagine the US not providing enablers like satellite targeting, etc. Or the US being unwilling to sell ammo.
Deals don't matter when the counterparty wont adhere to them and there is no third party forcing them to