Sen. John C. Calhoun famously opposed the Mexican War.
Calhoun was adamantly opposed to conquering and incorporating “All of Mexico” which some of the most strident American imperialists wanted to do at the time because he felt that it would poison the Union. He was later proven right about that and many other things besides:
“RESOLVED, That to conquer Mexico and to hold it, either as a province or to incorporate it into the Union, would be inconsistent with the avowed object for which the war has been prosecuted; a departure from the settled policy of the Government; in conflict with its character and genius; and in the end subversive of our free and popular institutions.”
“RESOLVED, That no line of policy in the further prosecution of the war should be adopted which may lead to consequences so disastrous. …”
The next reason which my resolutions assign, is, that it is without example or precedent, wither to hold Mexico as a province, or to incorporate her into our Union. No example of such a line of policy can be found. We have conquered many of the neighboring tribes of Indians, but we have never thought of holding them in subjection—never of incorporating them into our Union. They have either been left as an independent people amongst us, or been driven into the forests.
I know further, sir, that we have never dreamt of incorporating into our Union any but the Caucasian race—the free white race. To incorporate Mexico, would be the very first instance of the kind of incorporating an Indian race; for more than half of the Mexicans are Indians, and the other is composed chiefly of mixed tribes. I protest against such a union as that! Ours, sir, is the Government of a white race. The greatest misfortunes of Spanish America are to be traced to the fatal error of placing these colored races on an equality with the white race. That error destroyed the social arrangement which formed the basis of society. The Portuguese and ourselves have escaped—the Portuguese at least to some extent—and we are the only people on this continent which have made revolutions without being followed by anarchy. And yet it is professed and talked about to erect these Mexicans into a Territorial Government, and place them on an equality with the people of the United States. I protest utterly against such a project.
Sir, it is a remarkable fact, that in the whole history of man, as far as my knowledge extends, there is no instance whatever of any civilized colored races being found equal to the establishment of free popular government, although by far the largest portion of the human family is composed of these races. And even in the savage state we scarcely find them anywhere with such government, except it be our noble savages—for noble I will call them. They, for the most part, had free institutions, but they are easily sustained among a savage people. Are we to overlook this fact? Are we to associate with ourselves as equals, companions, and fellow-citizens, the Indians and mixed race of Mexico? Sir, I should consider such a thing as fatal to our institutions.
The next two reasons which I assigned, were, that it would be in conflict with the genius and character of our institutions, and subversive of our free government. I take these two together, as intimately connected; and now of the first—to hold Mexico in subjection. …”
It is not often appreciated by modern day “progressives” how much racism and white supremacy had to do with putting the brakes on American imperialism or why it came to an end during the Cold War. Historically speaking, “racists” and “white supremacists” have tended to oppose American imperialism because starting devastating wars in foreign countries and occupying them indefinitely has only led to the death and displacement of foreigners and their eventual migration here.
The failure of the “All of Mexico” movement is one example of this. The failure of the Grant administration to annex the Dominican Republic is another. The opposition to annexing Hawaii is another. The opposition to the Spanish-American War and the failure to annex Cuba is another. The Tydings-McDuffie Act of 1934 which granted independence to the Philippines is yet another example of this.
“White supremacists” have typically wanted America to be less engaged in the world for the United States could remain White and Christian. The Founding Fathers were “white supremacists” and their foreign policy was non-interventionism, peace and commerce with all nations.
Note: It goes without saying that “white supremacists” have supported settling and annexing contiguous territories. It’s also true that Free Soilism similarly constrained American imperialism because Northerners opposed the expansion of the South and vice versa. Still, there is a long tradition of “white supremacists” like Rep. John Rankin or Sen. James K. Vardaman of Mississippi opposing American imperialism and it has continued down the present day in the strident opposition of their descendants to the Iraq War and now war with Blompf’s plans to intervene in Syria, Venezuela and Iran.