Great War

As with OTL, WWI was refer as the "Great War", but there no indication that this term will or will not change for World War I after WWII as it did in our timeline. Like OTL it was fought between the Entente and The Alliance. But the addition of the United States to the Alliance and Confederate States to Alliance created an American front.

Campaign For the U.S
The Union main objective during the war was Louiseville Kentucky (and subseuqently invaded the State at the begin of the War. In the hope of crippling the Confederacy a invasion Sonora was attempt for objective the Confederate port of Guyanas. The invasion was a failure and the u.s were forced to retreat back into New Mexico.

Hoping not to repeat the mistake of the Second Mexican War Canada was invaded right away with major object Québec, Ontario and Manitoba. By 1915, the southern bank St-Lawrence was under U.S control, but the lack of troops made the invasion stall at Winnpeg, Manitoba.

United States were also victim of an uprising in Utah, the major railway lines in the state greatly help in the subdue of the revolt.

By 1916, The U.S army was able to make it's way from western Kentucky to west Tennesse. The Tennesse campaign saw the first use of Barrel. On the Canada side, The united States started to enter British-Colombia.

The Barrel Roll Offensive started of April 22 (Remembrance Day) 1917 in Tennesse, It was so successful that the United States were able to take back Washington D.C, severely cripple the Northern Virginia army. The U.S army finally had reached Fredericksburg, Virginia when armistice was finally declare.

At the end of the War the United States were holding from the Confederate : Sequoyah (Oklahoma), West Texas part of Sonora and Kentucky.

Aftermath
Contrary to OTL, in this ATL the Entente was beaten in 1917, leaving Germany and U.S standing as the leading world powers. Just like in OTL however, frustrations on the part of the losing side led to another war.