Keeping dollars flowing internationally and encouraging importation of cheap foreign goods is one of the ways they mitigate the adverse effects of money supply inflation. My efforts to find better boots and clothing have only revealed how expensive things really are when the veneer of prosperity is torn away.
On the other hand, there is the old adage that says when goods don't cross borders, armies do. Trade with China has curtailed the war hawks in both countries. Closing trade means their corporate cronies no longer have something to lose from war. Trump has had quite hawkish rhetoric regarding China, and while it's largely bluster now, who knows what would happen if that trade slowed to a trickle?
The answer is real free trade and consumer choice in money, but that requires breaking laws nowadays.