Actually, if Kerry gets his way, we wouldn't be fighting terrorists in our own country with our own guns. The minute some terrorist commits an atrocity using a gun, the Democrats will ban every privately-owned firearm in the U.S. It will be all about how a gun mysteriously caused a terrorist incident -- the left won't question about how terrorists got into the country, or how they got organized, or who is paying them, etc. Americans who defend themselves will be called part of "the culture of violence" and we will be told that if we are passive enough, the terrorists will go away.
In such a horrific scenario as you describe, then we would of necesssity be fighting all domestic enemies in the streets and in the hills at the same time.