Its none of Congresses business what type of car I buy.
True, just like it's none of Congress' business whether you wear clothes made in China, or buy furniture made in China. And it's none of their business whether I buy a computer made in Taiwan, or one made in Dallas. And if you're an auto maker, it's none of their business whether you buy your steel from Japan, or Pittsburg.
But they've made it their business, and I'm suggesting that if you're going to monkey with free trade, then you should at least do it in a way such that we won't get penalized by the WTO. If you tax luxury cars instead of European cars, then the WTO has no cause to complain. But the effect is pretty much the same.