This timeline authors are Fitzgarden, VENEZUELA and Darsksiderwow.
The divergent timeline begins after the Great War, when a growing "Regionalist movement" was strengthened by its adoption of an isolationist platform. Meanwhile, Prohibition failed as a constitutional amendment, polarizing the nation between "north" and "south" states. The result was an overall decline in federal authority as power shifted from the federal level to the state level.
After the breakout of a deadly strain of smallpox in America, states closed their borders, further dividing the Union. Shortly after the Wall Street Crash of 1929, Texas seceded from the Union, forming the Republic of Texas on January 1, 1930. New York was the next state to secede, and persuaded Pennsylvania and New Jersey to merge with it to form the New England State. California followed suit, as did Utah, which had already come its king. Likewise, America's territorial holdings overseas were surrendered following the nation's formal collapse and the formation of the Federal Republic of Columbia on March 1, 1932. In conflict with the federal government after the establishment of the Smith Law in 1928 that made Mormonism the state religion, Washington, essentially powerless, was unable to stop the country from falling apart. The federal government made its last stand against the 'People's Revolt' of the breadbasket states. When the US Army was defeated by the People's Republic of North America forces in 1931, the fate of the Union was sealed, and the rest of the country dissolved into independent nations by the end of 1932. In 1932, Wisconsin, Michigan, Illinois, Indiana, Ohio, and Minnesota secede creating The Free States of America. By the same time Arizona and New Mexico secede in The Republic of Aztlan, but North Arizona secedes in Navajo State. Louisiana also secedes and the other South States create The Confederate Dixie States of America.
Though not directly affected by the Texas Secession, Canada found itself dragged down by the collapse of the U.S., with Quebec seceding in 1930 and the rest of the provinces siding with their nascent southern neighbors: New Brunswick and parts of Quebec joined Atlantica (Maine, New Hampshire and Vermont), Newfoundland joined Quebec, Manitoba joined the People's Republic of North America as did parts of Saskatchewan, with the Lakota nation laying claim to the rest, British Columbia merged with Oregon and Washington in Pacifica and Alaska claimed the Yukon territories. The core of the former Canadian government established the Republic of Ontario. While Ottawa's authority technically extends to Alberta and the Northwest Territories, these areas are mostly no-man's land, Alberta and Saskatchewan secede in two republics, while Nova Scotia and Prince Edward Island comprise a self-governing body, commonly referred to as the Sea Association. Mexico was critically affected, so Yucatan seceded, later Sonora, and California invade Baja California. Meanwhile, The Appalachian Mountains secede in Appalachian Territory. Massachusetts and Connecticut secede as The Atlantic Coalition. Nevada, Idaho, Wyoming and Montana secede in The Western States of America. In 1931, the Territorial Government of Kingdom of Hawaii was left defenseless in the wake of the fragmenting country and was overthrown in favor of the monarchy with Edward D. Kawananakoa as the king. Likewise, America's territorial holdings overseas were surrendered following the nation's formal collapse and the formation of the Federal Republic of Columbia on March 1, 1932.
The resulting nation-states that formed were no longer unified — distrust between them strained diplomatic relations to the point that several small-scale wars broke out.
In 1933 the places that surrounded the Great Lakes secede from FSA, New England, and Republic of Ontario and create the Great Lakes Nation. Meanwhile, Southwest Outer Banks and East Dixie Confederation secede as New Afrika. In 1934 some parts of British Columbia and Pacifica secede in Cascadia Republic. Vermont seceded from the Maritime Provinces and created the Second Vermont Republic. In 1935 People's Republic of North America created a puppet state with the help of the USSR in ancient Michigan, Wisconsin and upper Michigan Peninsula called the North Star Republic. In May 1936 the Mexican Communist Party made a revolution which bring chaos to the country, so Chiapas and Chihuahua secede. Finally, the party established People's Republic of Mexico in Coahuila, Tamaulipas, and Nueva Leon. In January 10, 1937, some ex-Canada governments had a conference to decide if they should join The Commonwealth of Nations, the results were: the Commonwealth of Ontario, Commonwealth of Pacifica, and Commonwealth of Alberta. In July, the Alaska's People's Revolutionary Party made a revolution with the help of People's Republic of North America, North Star Republic, and URSS, and take power declaring. In September, The Republic of Carolina seceded.
After WW2 The USSR Occupied Asia and Eastern Europe creating many People's Republics and a Cold War starts between UK and USSR.
Mexico is on the same regionalist movement that USA had and possibly is also going to Balkanize.