Basically the only force capable of wrecking the USA is the USA itself. When the society fals appart fror some reason, the USA will desintegrate and fall into some small autonome erea´s of basically selfsustaining units, after some major disaster, like a worldscale natural disaster, or economical chaos.
To start with the later, the USA is a Federation of more or less independant states, only cooperating together on Federal issues, so a financial issue is not enough to lat all fall appart mosty likely. It has to be larger than that, something like a large scale depression, where the Federation cannot cope with the demands of the day anymore, due to shortages in financial issues and incompetence, or unwillingness of the memberstates to fill in the gaps. When the Federation cannot continue its Federal responsebilities, the Federation will desintegrate into more autonome, smaller units, starting with the states themseleves, but possibly falling appart further, as the states themselves wiol not be better of then the Federation itself.