China is the big boogeyman now that Russia is out of the picture and it's as Dusty
pointed out, a big stretch once you look into it beyond "Chinese," "billions," "military," "expansion/economic aspirations." China is in no position to invade us anymore than we are to invade them. Sure, we can toss nukes at one another but that's what M.A.D. is for. No one wants to start a nuclear contest because you're a loser too.
Terrorists don't count; they aren't a government (all the hoopla of government sponsored
terrorists aside) no one wants to be known for setting off world war 3 and killing 2/3rd's of the world's population, including their own.
So Red Dawn just doesn't work as the realistic threat we're supposed to be fearing. It won't stop someone from arguing otherwise or from getting a movie with a similar theme done a thousand times over though.