Oh? Look at machining costs in the US vs China. Look at the cost to get something punched or stamped or bent or extruded or skived.
We have a few companies that make a decent effort, it's true, and indeed the US sheet metal industry is one of the few industries that could be entirely self-sustaining if the ports closed tomorrow. But most of the metalworking in the US is just heavily subsidized six ways to Sunday and still uncompetitive.
........? North America and China are about equal in terms of steel and aluminum working expertise. Really not sure where you're getting that idea...