A good question. There are a couple of caveats to that:

1. Most Chinese exports to the US are consumer goods. Especially after the COVID pandemic reinforced the need for strategically self-sufficient vital industries. It would hurt, no doubt, and increase unrest, but it's not fundamentally crippling to the basic functioning of the economy. It's toilet paper and household good shortages... again.

2. Blocking exports to the US would hurt China as well. But more than that, blocking exports to the US would mean the US would pressure everyone we have influence on (ie a good chunk of the world economy) to sanction China in turn, which would be even more painful to their economy. China is the US's 3rd largest trade partner. The US is China's largest trade partner.

3. That would remove almost all incentive for the US NOT to intervene - ie if China is already trying to strangle our economy, how much more can they do, short of nuking us? In other words, Chinese ports would be blocked by USN battlegroups, and that's a LOT more deadly to the Chinese economy than 'No trade with China' is to the US economy. Not only that, but Chinese intervention to Taiwan would undoubtedly be assaulted by US forces in such an event, leaving China both strangled and its offense neutered.