Definition: Pacific Island nation and its capital of Manilla that came under American imperial control
after the Spanish-American War.
Philippine Annexation

Philippines is the pacific island nation which along with its capital Manilla was annexxed in American imperial control.

Explanation:

After the American - Spanish war, America found itself as an imperial power in the pacific and laid claim of conquest over the Philippines a huge nation in the middle of the pacific ocean.

The Americans had not been colonialists but after this war they began to sow colonial enterprises to cash in on the profits that other European powers were reaping from these prosperous lands they were ruling over with little more than the right of conquest to boot for themselves.

a would be the answer