For a post ARW PoD, have the states of the new USA refuse to give up their transappalachian claims to the federal government. No new states are formed beyond the original 13 but this leads to greater competition and conflict among the states on other issues as they jockey for power in the federal union. This results in the 2nd Constitutional Convention of 1801 in which the Federal Union is peacefully disbanbed, replaced by the recognition of the complete independence of each of the original 13 states within a general alliance known as the North American Commonwealth of Sovereign Republics. The disbanding of the Union is proudly signed by Thomas Jefferson, last president of the United States.
Areas under the control of the 13 states within the the NACSR is limited to areas east of the Mississippi River. Elsewhere, with the collapse of the Spanish Empire, Mexico and Florida become independent. In 1836, Carolinian colonists in northeast Mexico break away and form the Republic of Texas, and in 1850, Mormons fleeing persecution in the Republics settle in northwest Mexico, achieve independence and establish the Federation of Deseret, which grows to encompass all of the Great Basin and norhtwestern Sierras extending to the Pacific Coast. Following the War of Mexican succession, California also breaks from Mexico as another Spanish-Speaking republic in North America. In the late 1860's British North America is reorganized as four separate dominions: Quebec, Canada, Lakota, and Athabaskia - each granted independence in recognition of their service to the Crown in the Great War of 1905. Lakota (a landlocked federation in the central and northern Plains) is the only largely Native American political entity. After the 1924 Marxist-Communard Revolution in Russia, the Grand Duchy of Alaska becomes independent, Greenland achieves independence from North Germany in 1935, and after the Mormon Wars of 1930-45, Deseret is forced to grant independence to the Columbia-Cascade Stake (OTL Washington and Oregon)
By 2005 this results in a North America containing 12 independent states outside of the NACSR, which by itself includes 9 squabbling english-speaking countries (several have elected to form secondary political unions since independence from the old USA). Other than the 4 Domnions, which recognize King Andrew as sovereign and Alaska, which is ruled autocratically by Czar Alexander IV, the rest have adopted republican forms of government although they range from the very liberal and democratic to near fascist in how political power is actually implemented.
There are no major world powers in North America, but the continent is home to several substantial mid-level miliary powers and one major economic power. Had the Mormon Wars ended differently, no doubt Deseret would have dominated North America and assumed global power status, but that was not to be.