And Leon Trotsky, whose followers invented the idea, rather recently, that it is in any way conservative to have an interventionist foreign policy.
And just think of how fundamentally anti-conservative war is. The effects it has on our own culture could never be described as anything resembling conservative. Think of the changes that went on during the world wars. Families were uprooted from their homes; young men were shipped off to die in some unknown foreign land; those who stayed behind were forced to give up their family farms or small-town lives in order to earn a wage in the cities, with women now working in factories producing death machines in order to support their families. The psychology of the people was changed from one valuing individualism, free markets, and respect toward other nations, to one valuing big government, central planning, and a collectivist "us vs. them" mindset.
War and interventionism are just so fundamentally incompatible with traditional American conservatism.