If China was to attack Taiwan, now would be the time. The current world order is at least in part based around the notion of the US (and allies) having the military capacity to fight any plausible combination of foes at all times. That this military capacity was used in accordance to a set of rules with input from allies and partners made the system tolerable.

If the US lacks the munitions to fight all of these conflicts, and is unreliable to allies or foes leads to a high likelihood of conflict.