I doubt a large, standing army would be politically impossible. The reason Americans were historically against it OTL was there were few people who saw the need for one. All the Great Powers were across the ocean and would have a damn difficult time conquering the country. Now with its biggest enemy just across the border that would change and in a hurry!!
I still think it will difficult to justify, even with revanchanism, a near million man peacetime army comparable to that of turn of the century France, Britain, Germany, or Russia. That being said, an army 2 or 3 times the size of OTL's with a well orquistrated reserve system would probably be quite feasible.