The answer to an aggressive and militant China would be the same answer to any upstart nuclear power threatening the world - we have already seen how effective sanctioning Russia has been in the wake of their aggressive imperialism stints in the past decade. So successful as to inspire them to try undermining US elections to get an apologetic administration in place to remove said sanctions.

Sanctioning China economically though is a moralistic move. It has real absolute costs to the US economy, and such sanctions would need the broad consensus support the Russian ones did - if you don't punish aggression unilaterally and in global unison then the aggressor still has inroads into the global economy to ease any impact.

It is never a solution to spend several hundred billion more dollars on weapons of war that are wholly irrelevant to any legitimate threat of conflict with any other nuclear power. They only serve as a dick measuring contest of how much of your economic productivity you can wholly waste before your economy collapses. That is pretty much exactly how the Soviets fell, and the US is too egocentric to realize its going down that road too.