The military has an incentive to ensure there are plenty of Americans who know how to design and manufacture things. A truck and a tank have a lot in common - if war breaks out we want the ability to take people of of trucks and get them making things the military needs.
This is the same reason the Navy has for building ships in the US even though they can be done other places cheaper.
This is the same reason the Navy has for building ships in the US even though they can be done other places cheaper.