1776: Slavery is denounced in the Declaration of Independence.
1783: Treaty of Paris leaves Georgia and South Carolina as English colonies; However, the American Patriots have successfully grabbed Halifax and York. This leaves the United States with a northern border on the St. Lawrence. It also means that as the United States dumps slavery, this is a problem forced onto the United Kingdom.
1803: Louisiana Purchase.
1808: The USA passes the "Manumission act" phasing out slavery over the next two decades..
1812: War Scare of 1812 is handed by the Brits ending impressment of sailors and ending supply of guns to Indians.
1820: Indian States Act is passed in Washington; Native American Tribes are granted territorial status and the right to advance to statehood. Ongoing discussions will address borders and formalize native leadership into a democratic system. This also establishes the rule that all men can vote.
1848: Claims over Oregon Territory and a major slave revolt in British America lead to a war between the United States and the United Kingdom. Unexpectedly, this turns into a world war as Germany suddenly emerges as a unified country and chaos explodes in Europe. The UK is thus forced to deal with attacks around the world against its far flung colonies. In the end, the UK gives up on its Caribbean colonies, Georgia, Florida, and Alabama, as well as Jamaica, Bermuda and Barbados. Although the USA has gained all of the disputed Oregon Territory, it has returned control of occupied Canada to the UK as its primary concession to the Brits.
1873: Second Mexican Civil war breaks out; this is a beginning of the "Long Alliance" between the United States and what will ultimately become its staunchest ally, Mexico. US Intervention into the conflict, at the request of president Santos, will quickly stop the army warlords that are trying to carve up the country as well as Texan Slaveholders aspiring to build their own nation.
1881: Women granted the right to vote.
1906: Great War Breaks out--the USA backs the UK-German-Austrian alliance against France/Russia/Italy. The outcome is decided in about two years--a major triumph for democratic Germany, UK and Federalizing Austria against the likes of Napoleonic France, Czarist Russia and Millitant Italy.
1922: The USA establishes strong ties to the Republic of China, led by Hong Guo. With similar efforts from the Mexican Government, this democratic movement will ultimately defeat the multitude of warlords that have emerged in the fall of the Qing dynasty.
1945: The United States, as the lead proponent of anti-colonialism, commits itself to an alliance against colonial powers. Germany, Austria-Hungary-Slavonia, Mexico, and the RoC support an effort by the Japanese to rebel against their British occupiers.
1955: The UK decides that it is time to dismantle the British Empire; under heavy pressure from Germany and the USA, the UK pulls out of Transjordan, India and Egypt.
There we have it, USA that never colonizes, treats its natives most generously, and is a major good guy. Its borders are also rather crazy...