Final answer:
The U.S. annexation of the Philippines was partly influenced by the strategic desire to expand naval power in Asia and to open trade markets in China, in line with military and industrialist interests.
Step-by-step explanation:
One reason for the act of U.S. imperialism, as exemplified by the annexation of the Philippines after the Spanish-American War, relates to the strategic interest in expanding American naval power and influence in Asia. The victory at the Battle of Manila Bay, where the U.S. Navy, under the command of Commodore George Dewey, destroyed the Spanish fleet, aligned with the vision of Alfred Mahan for the U.S. to have additional naval bases in the Pacific Ocean. This strategic positioning was not only for military strength but also supported the industrialists' desires to open markets in China.