This provision is being pushed by the American steel industry — which is odd because the American steel industry is actually very competitive on the international market. Steel once defined the why the Rust Belt was called the Rust Belt. It had to entirely re-create itself with new technology and is now renowned for its quality/price.
Patriotic marketing efforts like this have been going on forever (the Brits tried a “buy Commonwealth” campaign during the last Great Depression and Detroit has tried it several times). They always fail because they try to fly in the face of the consumers’ best interests.
Either your product is competitive or it isn’t. If it is then an appeal like this isn’t needed (though it can’t hurt). If your product doesn’t offer a value the consumer wants (ie, it’s over priced or ugly or doesn’t work well) then adding patriotism to the mix isn’t going to do a damn bit of good.
American Apparel succeeds not because it’s made in the US but because they’ve combined design, quality and price in a way no one else has AND they’re putting themselves out there as a non-sweat-shop operation. Without the first three items the fourth wouldn’t matter in the least.