the United States first line of defense against an armed invasion is a redneck in a pickup truck with his hunting rifle
The first line against invasion is a military complex which spends more on "defense" than the rest of the world put together, rednecks in pickups would just get in the way.
They're as relevant to U.S. national defence as the duke of Norfolk's obligation to provide 150 pikemen and 50 archers is to that of the U.K.