Texas? No, not really. Texas defeated Mexico (which had won independence from Spain about 15 years earlier) in a revolution of its own in 1836. Many, perhaps most, of the participants on the Texian side were immigrants from the US, but many (including a number of those who died in the Alamo) were Spanish. Guantanamo? No, not at all. The US enclave at Guantanamo Bay is held under a lease - the validity of which is disputed by the current Cuban government, of course. New Mexico, Arizona and California? Yes, probably. These areas were taken by the US in the War with Mexico in 1846-1848 and ceded to the US in the Treaty of Guadalupe Hidalgo...kinda like Quebec, eh? The Paha Sapa? No more so than any other region seized from the Indians in violation of a valid treaty.