How about France feels threatened by the new Prussian state, leading them to declare war in 1872 or '73. England, being longtime enimies of France, become allies with Germany and from a more Prussian type military, defeating France combined by 1874 or '75.
France becomes incresingly Fascist after this war, leaing America to become wary of it. For some reason, the SA War is butterflied away.
America sees the Anglo-German alliane as a rising power, and POYUS Grant makes an official alliance by 1882.