Final answer:
Spanish officials were concerned about losing control in East Texas primarily due to fears of American expansionism, which threatened Spanish sovereignty and economic interests in their New World territories.
Step-by-step explanation:
The question 'Why were Spanish officials concerned about losing control in East Texas?' pertains to the historical context in which Spain found itself following various global and local events threatening its hold in the New World. The correct answer is C) Fears of American expansionism. Spain had multiple concerns about losing control over its territories in the New World, particularly due to the aggressiveness of American expansionism. Given the United States' support for revolutions in Latin America and its recognition of revolting governments in order to undercut European influence and assist commerce, Spain feared that American expansion could lead to a loss of its territories. Additionally, the close of the Mississippi River to American traffic and the encouragement of settlers in Kentucky and Tennessee to act independently, further indicated that American westward expansion would threaten Spanish control over its borders and economic interests.