Why did the mexican government worry about the loyalty of new settlers

Por que ellos son codos!

If you are referring to the time period when the Americas we're expanding, then this includes the time Mexico opened its borders and let everyone in because they needed money. They were worried because Americans were known for taking land, so they weren't so sure about their loyalty ... Then when so many Americans clumped up in a part of Mexico (present day Texas), they revolted, trying to claim the land for America. This caused a war and you should know what happens after ...