The US didn't really have any elite interest in
The US didn't really have any elite interest in expansion outside of the Western Hemisphere (and, indeed, outside of North America) for much of the Nineteenth Century, however.
Building the nation itself, and then the confrontation over slavery, really defined the most significant interests of the US for more than a century; the territories purchased or annexed from Lousiana in 1803 to the Gadsden Purchase in the 1850s were not very densely populated and so were open to "American" settlement; the same held true for Alaska, which, along with Hawaii and Panama are, essentially, the corners of a defensive triangle seen as sheilding the Pacific Coast. Hawaii, of course, although fairly densely populated, was dominated by Protestant whites, and even the native Hawaiian population had been largely evangelized by Protestants by the time US elites seriously began considering annexation. The eccentricities of Nineteenth Century racism are tangled, but they are there...
Obviously, the basic questions of absorbing large and generally non-protestant populations were enough to dissuade any major annexations of heavily populated territories in Mexico or the Caribbean in the Nineteenth Century, as well, especially since economic domination was presumably always going to be cheaper than legal annexation; the liklihood of any interest in populated territories in the eastern hemisphere was just about nil.
Liberia, after all, was set up as a freedmen's colony; essentially, as a place to
send a population elites in the US did not want to remain. Annexation doesn't tie in with institutional racism, basically...
For good or for ill, Guam and Samoa amounted to coaling stations; Puerto Rico an afterthought to Cuba and potential defensive bastion at the east end of the Greater Antilles; and the Philippines is the one real exception that proves the rule, notably because (however sincere or not) the stated goal in the PI was eventual independence. The fact that the PI was never a territory (in the sense of a legal status on the path to statehood) makes that pretty clear...
The one place I could see the US staking a claim outside of the Western Hemisphere in the "imperial" era they really did not, paradoxically, is Antarctica, although that would be a Twentieth Century development.
Best,