Why did americans begin to settle in the southwest after mexico declared its independence from spain?

 Americans started to settle in the Southwest after Mexico became independent because US officials declared that they will protect the people that are going to migrate, and also it was much easier now because Mexico on it's own was not powerful enough to cause any troubles and invade the territory of the US. Also the Indian tribes were already put under control and free land was given to the new settlers. All of those were a big motive for migrating to this part of the country.