one problem i noticed is with the US actually spending their MPPs on the most difficult setting. after an early sea lion, i was faced with a russian horde to deal with (3 tiles deep in the north). the US tried to free the british isles with an amphibious attack (no HQ support) that surprised me, but after that, they did nothing. at the end of the game, they had over 6000 MPPs, yet they still had strength 5 army's guarding NYC.
russia also seemed to give up building units once they ran out of corps/armies to build. they didn't ever build a tank/fighter group/rocket nor replace them if they were destroyed. the russian AI tends to concentrate almost all of its forces in the north now, instead of attacking north and south. i purposely left the bulgaria undefended yet they never once made an approach towards that sector.