This is demonstrably false. Nukes have allowed those who have them, to bully (wage asymmetric warfare on) those who don't.
Would the USA have been so cock-sure about murdering 5% of Iraqs population, if it didn't have nukes?
The US was very clear in not attacking Iranians, though Iranian support was the vehicle by which US troops were attacked. Iran got a measured response for its allies because Iran 'carries a big stick'
Air or missile strikes against US territory are very difficult to pull off. Only China or Russia would have any chance to overwhelm US missile defenses. Anything small-scale would be answered by conventional strikes and a ground invasion. No nukes are warranted unless entire cities get slagged or nukes or biological or chemical weapons are used.