Final answer:
Spain shut down most of its Texas missions in the 1770s due to the aftermath of the Jesuits' expulsion, the strain of maintaining control amidst Latin American revolutions, and political conflicts with other European powers and the United States.
Step-by-step explanation:
Spain closed most of its missions in Texas in the 1770s due to a combination of political, military, and economic pressures. Multiple factors, including the expulsion of the Jesuits, the rise of revolutions in Latin America, external conflicts with other European powers, notably Britain, and the increasing anti-Spanish sentiment in the region played a role. These pressures led to a reevaluation of the Spanish presence in America, and in Texas particularly, the missions were seen as unsustainable.
The expulsion of the Jesuit missionaries in 1767 caused unrest and contributed to the weakening of the mission system, as the Jesuits were significant in managing relations with the Native Americans and edifying the Creole elite. The outbreak of Queen Anne's War further weakened Spain's hold, and Spain's concern over its empire was exacerbated by the growing influence of the United States, which recognized and supported the new republics that emerged from the Latin American revolutions, undermining Spain's control. In addition, Spain's dealings with Great Britain and the United States were strained, complicating their efforts to maintain their missions and colonial presence in North America.