What caused the us to join the allies in ww1? ?

The Germans decided to resume unrestricted submarine warfare, and the Zimmerman telegram which suggested an alliance with mexico

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