America, instead of becoming a freedom loving country, becomes a militaristic imperialist Empire which invades and destroys other countries.
Birth of the Empire.
The Revolutionary War was different from the real one. George Washington was much more brutal and unkind. All British troops captured were executed. Anyone who opposed him was killed. During the war he also came to think that America should become an empire and destroy anyone who was against it. The war was won just as in real life but instead of creating the United States he created the Terran Empire. Washington became its Emperor. The other founders of the Empire like John Adams, Benjamin Franklin, Thomas Jefferson, etc, were all power hungry and wanted power. They were unkind - mean - horrible.
The Empire expanded west annexing more and more territory. It murdered millions of Native Americans who were poorly treated. Many of them were used as slaves. Citizens of the Empire were made to believe that they were better than the other peoples of the world. In 1779, Washington was poisoned by Jefferson who then became the new emperor. This would happen a lot in the empire - people would move up in rank by assassinating their leaders. The Empire had no mercy on anyone. It would eliminate anyone who oppressed it. It was built on slavery.
The war of 1812.
By 1812 the Empire looked to Canada to expand but Canada was ruled by the British. Meanwhile, Britain was at war with France at the time. As a result the Empire took advantage of this and invaded Canada. The British fought bravely. However, they were outnumbered and were beaten. As a result, the British were forced to cede Canada to the Terran Empire.