And you think the US will somehow magically stop supporting them if Iran effectively wipes them off the map by hitting their vital infrastructure?
We (Iran) cannot fight back against the US. Yes, we can hit US military bases, destroy their aircraft carriers, etc. But at the end of the day, Iran has no effective way of hurting the US mainland while the US can and will do that.
The US nuclear arsenal has a destructive power of several giga tones. Even if we assume Iran has nukes, or will develop them immediately, our destructive power will hardly reach even one mega tone.