Interestingly though, there WERE concerns in President James K. Polk's administration about how Europeans and others might view the end result of the Mexican-American War in 1848. It's part of the reason the captured lands (California, Arizona, Nevada, etc.) were technically purchased from Mexico rather than simply snatched and annexed. I'm not sure why they feared the Europeans would be angry about it a ton, unless: 1. It would in their view upset the balance of power in the world or 2. It would make America look like a hypocrite for practicing methods similar to European empires against fellow "New World" countries. It unquestionably helped lower anger and tensions between the US and Mexico though after the war though (since the lands technically were not stolen).