With the ThelegendofEarl elite machinima put up.
Notice at the end where the 2 soldiers were in MW3.
Notice that they are both US Soldiers. (Probably)
Since all of the Call of Duty Games involve teams v teams (SF.141. v Spetsznaz) (US Rangers vs Blahh blaah blahhh)
You can infer that their will be a more than a WW3, there might be a war within the states!
just a little Theory I made up. :)