Answer:
The main problem is that Spanish Texas was sorrounded by a fast-growing and fast-developing country to the North and East: the United States.
Step-by-step explanation:
While Spanish Texas was very sparsely populated, and did not attract enough settlers to drive the Native Americans away from the territory, or to build a well-functioning economy, the United States was receiving new settlers every year, who were pushing farther and farther west, to the point that they were starting to settle in Spanish Texas.