You guys do realized the state of the current middle east, the advent of WW1 and WW2 was very much a byproduct of western imperialism right?
Then again, Japan was an asshole as well back in the imperialism era and the rape of nanking is still too fresh in the collective social memory.
As for China, there's still a long way to go for it's military. Their spending is a mere fraction of the US in terms of percentage of their capita GDP. Not forgetting military institution wise, it's nowhere near the level of experience that other major powers have. It's going to take them awhile longer and better experience than fighting rioters.
Granted, the US economy have been battered by their last two wars. The UK is not the superpower it once was during the world wars. It's going to be pretty crazy if China decided to mobilize. Japan is probably going to be banker for the western power if that ever happens.