His statement implies that buying only American-made parts is good not just for the particular Americans who make and sell those parts, but for all Americans—indeed for America as a whole. But that can’t be true. Sure, it is good for those who make the parts, but it’s bad for unidentifiable other Americans, and that means it can’t be good for the whole country.

Observe: if Lindell bought foreign-made parts, he would pay for them with dollars. But his foreign vendors can’t spend dollars in their home countries, just as Americans can’t buy groceries with Japanese yen, Chinese yuan, or euros. Foreign vendors, however, can use dollars to buy American products or invest in the U.S. part of the world economy. The only other thing they can do with their dollars is sell them for their home currency, but then the buyer of those dollars would face the same choice to buy American products or invest in the United States. (The so-called trade deficit equals the dollar amount of the investment in America that foreign exporters undertake. That deficit is no problem, Messrs. Trump and Sanders.)

So if Lindell really buys all his parts from Americans, other Americans lose out because some sales and investments don’t happen. When doing economic analysis, the French economist Frederic Bastiat taught, look for the unseen as well as the seen consequences.

I don’t mean to criticize Lindell. My point is that his implicit message—that Buy American is good for all of America—is untrue.