See, now, the thing with nukes is that only one of two things can happen when you use them on people:
1) Everyone imposes sanctions.
2) Everyone attacks you.
Now, for America, sanctions mean bull-****. Every piss-poor country would clammer to defy the sanctions in the hopes of securing a long-term trade relationship with the US. And once everyone knows you're willing to nuke people to win, they're very hesitant to attack.
The only real thing they can do is initiate the 'proportional response' contingency whereby everyone launches all their nukes in the hopes of annihilating all your nukes before you can launch them.
So basically, if America were to irradiate the middle-east, there'd be ****-all anyone could do bar total nuclear holocaust.
Let's not forget that any conventional attack would be somwhat hampered by the fact that to run the tanks, planes and choppers people would need oil, which, conveniantly, would be situated below a giant, super-radioactive crater.