I don't understand why people keep thinking the entire East Asia will be against China. Afterall, these are China's neighbors. It would be insane for anyone to think that China would be completely annihilated. So even China loses in a future conflict, these small nations will still have to deal with China, a HUGE nation sitting next to their door step. It would be much easier for China to harass them than the US to protect them. The harassment, of course, would include everything from military, social, to economical. It would be a nightmare for everyone involved, including China. However, if China is bent to avenge its defeat and is willing to absorb financial losses, those small Asian nations will have some difficult days ahead of them. China can't do anything to the US, but can easily do whatever it wants to these small nations in Asia. We all know how difficult it would be to live with a neighbor who has a grudge with you, let alone a neighbor that is at least 10-20 times bigger than you...
I think what most of these nations are doing now is to get the most benefit possible from both the US and China by pitting one against the other. When both biggies want bigger influence in the area and want to ally with you, you can negotiate better deals and get bigger interests. At the end of the day, no one is actually looking to help another nation. what every nation is doing is to maximize their own interest.
Unless they are attacked and have no choice but to ally with someone, they will most likely stay out of the fight. And once the fight is over, they will be friends with both again. Think about what you would do if you saw a grizzly bear fighting a Siberian tiger while hiking in the mountains. Would you jump in and help one of them, or would you stay behind and watch? I know what I would do: stay far away and watch.
I've mentioned this before and I'll say it again here. Asia does not hate China!!! There is NO hatred of any kind between China and Asia. SK, Japan and those ASEAN nations are NOT planning to destroy China whenever they get an opportunity. Yes, they may have some grudges and some disagreements, but nothing more than what neighboring countries anywhere on this planet are experiencing. If anything, there is probably more grudges between the UK and France than anything between China and the rest of Asia. DO NOT make it sound like the entire Asia will jump on China's throat whenever they see fit!!!