Well, of course, the US did have colonies throughout the Pacific and in the Caribbean. Some like a lot of the smaller islands were simply claimed and occupied like Midway. Others like Hawaii had more complicated conquests like Hawaii and American Samoa. In other cases the "colonies" were gained via war, especially the Spanish American war including Puerto Rico, the Philippines, and Guam. Other colonies were purchased like the Virgin Islands and Alaska... and Louisiana.

Which brings up the next major point. The US didn't need overseas colonies, they were busy colonizing the vast territories of North America. Just about every reason for picking up colonies could instead be satisfied via western expansion. Land and resources were both highly available much closer to home. Why send people across the world to settle the Transvaal or Queensland when Kansas and Oregon were "empty" and ready for settlement? Why go to the Congo for minerals when the rich mineral fields of California and Colorado beckoned? Why flee to Guayana when you can avoid religious prosecution in isolated Utah?

Interestingly the period when the US actually did start picking up overseas colonies follows closely on the heels of the official "closing" of the American West. Once the continent was surveyed, claimed, and homesteaded, the country started getting a lot more interested in foreign lands.