Though if you actually want to support America, I'd suggest you buy from the foreigner that's most likely to hoard and never spend your USD: that would mean America would get to consume some goods and services in return for ink and paper (or these days, 0s and 1s.)
The Fed targets inflation. A dollar hoarded might as well be burned. So they'll just replace it with a fresh new dollar.
(And if the foreigners eventually spend the dollar and it comes back to the economy you know and love, that's not much different than if you had spend the dollar directly in America in the first place. America just got an interest free loan of some goods and services while the dollar was abroad.
If enough dollars flow back to impact inflation, the Fed will shrink their balance sheet to accommodate. Ie they'll sell government bonds from their inventory to soak up excess dollars.)
The situation is slightly different, if you eg want to support your very local economy, eg your brother-in-law's company, or your city, your county or your state. Because the Fed target inflation in the whole country, not in one specific location.
