Well, experimentally, it's impossible, because of human nature. But theoretically, if extremely lawful people were appointed, that's one way. Another is if they had a serious reason to (like if they were given a legitimately extreme threat) and one more way is if there were one council or group to monitor them. the problem is, the council could become corrupt as well, and that system has certainly been tried.
The most lasting effect of the war on Mexicans was psychological. A tragic loss of soldiers and battles, the humiliation of having their capital and much of the country occupied by enemy troops, and the ignominy of a peace treaty that alienated half of the national territory (counting Texas) was a severe blow.
Kentucky was a border state during the Civil War.
Thousands of men chose to enlist in the Union Army.
