Also don't forget a lot of people have an economic stake in the military-industrial-complex and they instinctively know if you practice a policy of non-interventionism, there's good chance the military is probably not going to need you, ergo you're unemployed. Well there are a lot of people who join the armed services to avoid that fate or keep themselves from working as a fry cook back in their hometown Burger King. There area a lot of communities who don't want to see their bases shutdown and be reduced to welfare dependents (ever though their livehoos are already dependent on government in one form or another)
So on the one hand you have people who think the U.S. should be the ruler of the world regardless of cost and regardless of whether we can afford it for nationalistic reasons and there are others who feel the same way for economic reasons. Put the two together and it's a pretty powerful combination, especially in the South or in areas which have lotes of ties to the M-I-C or who have high numbers of vets.