The net effect, to the surprise of most, has been what appears to be a decline in the structural unemployment rate in the United States over the past quarter century. Protectionism in all its guises, both domestic and international, does not contribute to the welfare of workers.
At best, it is a short-term fix for a few workers at a cost of lower standards of living for a nation as a whole. Increased education and training for those displaced by creative destruction is the answer, not a stifling of competition.