The United States has a much more expansionist outlook during the 19th century than OTL. The monarchs of Hohenzollern-Amerika royal family would try to follow the footsteps of their Prussian, later German, relatives.
During the Canadian Revolutionary War, the United States would intervene in favor of the Patriote Movement (Lower Canada) and the Republic of Canada (Upper Canada) after the rise of American nationalism and border conflicts with Britain. The U.K. reluctantly decides to release the territories and the two states unite into a single Canadian republic. By 1842, however, the Quebecois grew resentful of the Anglophone Canadians and re-declared their independence. The remaining Canadian republic decided to join the United States as the U.S. states of Niagara and Superior.
As a result, several OTL Canadian politicians from parts of Ontario would be prominent American politicians in ATL.
World War II is much more European based as the allies would have to contend with three major powers fighting against them. This would allow for Japan to expand with virtually no combat against any of the major allied powers.
Japan and the United States would combat each other between 1941 and 1942, however President Al Smith would offer Japan a peace-deal if they decided to help fight the Axis Powers. The U.S. and Japan would lead joint-attacks on French Indochina and the British Raj; albeit very little cooperation and respect towards each other were seen.
Due to an earlier American entrance in World War I and the war being much closer to home, the Socialist Party would appeal to the lower class during and after the war. The Socialists would capitalize on the Department of Justice targeting unions, antiwar activists, and socialists in order to gain popularity.