History Learner
Banned
Source? This is immensely interesting
Woodrow Wilson and the Mexican Interventionist Movement of 1919 by Clifford W. Trow, The Journal of American History, Vol. 58, No. 1 (Jun., 1971), pp. 46-72
Marshall would need a casus belli in order to declare war, and given that the war in Europe just ended I doubt that many US politicians would want to start yet another one in Mexico without an outright Mexican attack on the US.
They already had one because the oil companies were freaking out over possible nationalization and the GOP was onboard with this; Senator Lodge of Anti-Versailles fame was the one who said that if they could not annex it, they'd arrange a "Cuban relationship" with Mexico.