For far too long, the fixed pie fallacy was the most widely held belief. When wars over resources were too costly to fight, society (not understanding that the ultimate resource is the human mind) went back to the good old trade wars of the mercantilist era. But something changed after the Second World War when Japan took a different path.
When it comes to trade, the best US policy, or that of any country, is the elimination of all barriers to imports. This can be done unilaterally. Abundance should always be preferred to scarcity.