This excerpt from an article on Americans abandoning U.S. automakers provides an idea of just how ignorant one would have to be to believe that "buying American" makes any sense:
Justin Watson, a 25-year old laborer and student from Beaumont, Texas, says he is fiercely loyal to American cars."My great-grandfather, grandfather and father fought against these people," he said of countries that are leading competitors of American automakers. "We're killing ourselves by buying their cars. I drive a Dodge truck, and always buy American."
(Internal link mine)
