Texas is obvious. Sam Houston is rebuffed by Andrew Jackson (in ATL head of the CAS) initially in OTL and decides not to try anymore as Britain offfers to accept Texan imports of cotton, as an alternative supplier to the CAS states, that broke with Virginia and North and South Carolina under the Articles of confederation as these states focused too heavily on tobacco production and were not sympathetic to their exports of indigo or cotton. One of their grievances in particular was politician John Calhoun's assertion that what was the state of Georgia then was a "filthy place founded by dishonest debtors". British prodding helped as well. Pennsylvania with its large German population, the tax on whiskey that Alexander Hamilton had threatened to levy, and its large rural areas that were unable to export grain due to a lack of canals and a lack of interest on the part of any state governors gain de facto and eventually de jure independence from the government under the Articles of Confederation. Massachusetts with its large shipbuilding industries and New York with its long time role as a port both yearned for commerce with the outside and also wanted to protect their infant industries. The southern states' general preference for low tariffs to induce a reciprocal English purchase of their cotton and other cash crops also angered farmers in Massachusetts and New York who wanted money from a high tariff to fund canal projects and to protect local farmers who did not produce cash crops. Thus New York and New England declared independence. Canada's Newfoundland area saw an opportunity for better access to fishing and less British interference in general, and thus threw their lot in with the New Englanders in a rebellion. Quebec, sensing English weakness and still remembering its French past declared independence as well, becoming the only french-speaking nation in North America. England's preoccupation with Napoleon in Europe facilitated all of these events by preventing England from doing anything about them. Spain retained possession of Florida and Cuba along with seizing Jamaica and the Bahamas despite its loss of territory to Mexico. Arizona, home to a large native American population separated itself from Mexico as did California in 1848 with news of gold. Russia extended its Alaska territory claims to what had been part of British Canada, down to the little town of Vancouver and received a promise of non-interference by the restless and fast growing Californians. The only part that Britain retained in its entirety was Ontario province, landlocked except for a route via the St. Lawrence river to the Atlantic that was controlled by pro-France Quebec. In short, Britain got really screwed over.
That is my stab at this.