they have done so in the 80's or right after the Cold War had ended? And also think about how many wars the US have successfully fought since the year 2000. 

As for US losing international support, it NEVER had and NEVER will have any international support for Taiwan secession. You might make a very strong argument that China would lose international support if she invades Taiwan and forces the unification but not the other way around.

While I would not rule out a serious incident at sea such as war ships colliding or mock dog-fights, but the past experiences have taught the US China would NOT back down. The Bush (jr) adminstration certainly learned it the hard way in its early days and back then China was much weaker vis-a-vis the US. The other thing to keep in mind is that China is a peer competitor and much of the provocations orchestrated by the US are closer to the Chinese coast. If a war breaks out, it does pose more danger/destruction to China. It also makes it much easier for China to rush troops and assets and supply them. The vaunted first island chain is much a barrier to China as it is an obstacle to the US. IF the US is really and seriously planning a war with China, you would see months of serious ramping up in military supplies and logistical upticks across the region especially in its bases on Guam and Hawaii. By then, anyone with a sub-80 IQ can see a war is coming. Until then, relax and don't get unnerved by the shenanigans.