What war was fought by the united states in the 1900

Well, the earliest war during the twentieth century was World War I, but if you're asking about 1900 specifically, I'm not sure if there was any officially declared war that the United States was involved in. Later, World War II and the Korean and Vietnam Wars ensued.

It developed as a reaction to the impact of european colonialism in africa on peoples of african descent. in the  mid-20th century, activists in africa adopted pan-africanism as a rallying cry for independence from colonial rule. some african pan-africanists sought to unite the continent as one independenthope it was useful