Answer-
This is a short cited policy because ultimately these laborers are themselves consumers. Ultimately they have to pay higher prices for these goods. Furthermore import substitution can't save them. In reality export promotion of goods in which usa has comparative advantage is in best interest of labour. But other countries will apply tariffs on usa exports if there own exports to usa are charged a higher tariff rate. Yes it depends on model of trade E. G in H-O model it is completely wrong to do so whileas as per some other models like Mercantilists it is quite good
Use graphs if needed. 2. The US labour unions, which mostly represents blue-collar workers (not professionals...