If you look at the years of the states and write down the ones in 1889 and 1900, it gets easier. Three that I got were Wshington, Montana, and South Dakota (I'm sure there are more but those were three).
The group that benefited the most from gaining independence from Mexico are the Tejanos who were the former Americans and has now become the American citizens and had claimed for the American rights and privileges.
It was mostly for new land trade and to convert the people in the Americas to the Christian faith
I believe it was Kent R. Weeks<span> </span>
Another way your question could be framed is “why do nations use imperialism on weaker countries?” and the simple answer is there are several motives such as ethnocentric purposes, religion, access to natural resources, expanding power, etc. Specifically people resort to imperialism on weaker countries because they are vulnerable to accept whatever helps the people survive in times of unrest.
