2/3 unionized auto makers in the US failed and had to be nationalized in order to survive. (Ford survived largely on the principle that you don't have to outrun the bear, just your hunting companions.) The foreign, non-unionized auto makers have no problem keeping plants open in the US and turning profits.

It may be more affordable to support a unionized workforce in Europe just because European countries have more generous welfare systems, or because European unions own stock in the company and have a financial incentive not to completely destroy the host. Of course, UAW resisted that level of responsibility in the GM and Chrysler bailouts.