But we can't just flatten out the land, that's immoral. We have to surgically kill the enemy so that we destroy homes. /sarcasm
That's how America is fighting right now. If we wanted to, we could've ended all our "wars" already.
On the topic of thermonuclear war, there are countries with the capabilities to launch at us from the Gulf of Mexico or East China Sea even, with guided rockets. We're not the only superpower and we aren't the only country with friends. China is at an advantage because they have a superior missile defense network. Syria has even more advanced weaponry but lack ground forces like Russia or China. In all honesty, right now Russia doesn't like us. Putin is very upset at how we handled things in the past, and the Olympics, and mock us for it every day. Not to mention, ICBMs from Syria are also more potent (they can carry payloads of EMP and/or gas). While they might not understand things like we do, you saw that video of those rabbits and Sarin gas, right? Yeah, we might be strong, but we're still vulnerable. Simply, an EMP would take us back to the Stone Age, leaving us open to ground insertion by any number of invading forces. We're too cocky and some day we're gonna learn that we're not the biggest, most elite force to be reckoned.