The idea is that any war against China would include Japan and Australia. Perhaps even the Philippines, Vietnam, and India.
The US wouldn’t be fighting alone.
However, if we don’t stand up to bullying by China then our security agreements with all our allies would be weakened and make war much more probable.
The long and short of it though is economically China can't afford to go to war short term gains maybe, long term defeat. They will posture and bloviate but in the end they will always back down.
Lots of times big guys don't know how to fight, everyone doesn't mess with them because they are big thus they never learn how to fight - this is China. The US on the other hand is a big guy who knows how to fight as we are always warring with somebody