I do believe that the US has so many strengths IE: bases and troops all over the world, the worlds strongest Air Force, and last but not least a supreme ground fighting force, both legs and mechanized units within the Marine Corp and Army.
And as far as someone using our own WMD against us I don't know alot about them but I am sure there isn't just an on/off button to launch them, it probably takes several people to fire a Nuke and good luck getting all of them to cooperate to launch one if someone had invaded the US.
Anyhow that is my opinion, take it for what it is worth.