Gamers Nexus just talked to some PC manufacturers about this.

"We assemble PCs, made in America from these parts"

(motherboard, CPU, graphics card, PSU, ...)

So what if, for example, the motherboard manufacturer moved to the US?

Well that's an assembly of a hundred or so other Chinese components. And the equipment needed to manufacture it would need to be imported.

Ok, but what if all those hundreds of factories were built in the US?

Well, they all use imported aluminium and steel and plastic, etc., and require their own imported machines to produce...

"Is any part of your PC entirely made in the US?"

"The shipping labels? And maybe some packaging"