i have only finished the gla missions but im on level 5 on both usa and china and just haven't finished them, sadly
--------------------------------------------------------------------------- "fighting for justice or evil is just fighting for no purpose really and just for the fun of it but to fight to protect the ones you love is to fight for a true purpose"
Anyways, I too had that problem, Cyber. I have had to restart the game multiple times.
Anyways, I have finished the GLA campaign and USA campaign, and gotten to the last China mission (Damn, it's hard, they don't give you enough time to build up your forces.)