The decline of Detroit UAW auto industry definitely weren't outsourced. It certainly wasn't GM that opened car factories in Japan and Germany. And it certainly wasn't GM shareholders or executives that benefited from the rise of Japanese and German imports.
This isn't outsourcing, this is simply a case of American carmakers being outcompeted by better products from Japanese and European competitors. (A significant fraction of which were actually assembled in US-based plants owned by those overseas competitors.)
This has nothing to do with "mobility of capital", and unless you shut down trade completely, there's nothing in the world that can protect poorly managed American companies from foreign competition. (Nor should you, while one million UAW workers saw their pay decline, 300 million Americans benefited from a vast improvement in car reliability, affordability and safety.)