This is a new timeline, trying to merge a few separate ideas into the most plausible version of events I can. Any constructive critiques and helpful suggestions and maps/flags are welcome.
The short version of the premise is:
Admiral Vernon heads to Havana after Portobello, and captures it unawares, leading to the fall of Cuba; Cartagenas de India fails to fall, but in the aftermath of the war, Cuba remains British. The Treaty of Madrid solves remaining issues from the war, resettling the Spanish into their other colonies.
After the Seven Year's War, Spain fails to retake Cuba, which closens ties to mainland North America, particularly the southern colonies, while at the same time diversifying its economy to prevent a collapse in sugar prices, with rum, textiles, and fishing industries.
Due to a misunderstanding, the Quebec Act is harsher than OTL, leading it to drive the Quebeckers into the patriot fold, along with Nova Scotia. Patriots manage to capture Bermuda and the Bahamas, but not Cuba, despite their best efforts. A small French-American War leads to the loss of St Pierre et Miquelon near the end of the 18th century, while the British lead a successful incursion into the Rio de la Plata for additional settler colonies and trade protection. Following a war with the new United States, Britain loses Cuba, but keeps Newfoundland and Rupert's Land, sending additional settlers to South America, South Africa, and Australia/New Zealand.
Texas declares independence in 1836 from Mexico, followed by the Republic of the Rio Grande in 1840, which allies with Texas in return for recognition of the Rio Grande as their mutual border. By 1846-8, the Mexican American War is negotiated with the cession of all of California, New Mexico, Sonora, and Chihuahua. The next decade in the US is spent assimilating the new territory, with new immigrants from Europe encouraged to settle here, leading to a wealth of new towns. In a series of wars from 1806-56, the United Kingdom cedes 52° and south of Columbia to the US, while it grows its territory in South America over OTL Chile, Argentina, Paraguay, and parts of Brazil. Hanoverians settle in numbers in British South America.
In Europe, much of the 19th century runs the same course, although the scramble for Africa is given to different territories with a slightly higher emphasis on settler colonies. (anyone have any ideas for a different African division, feel free. I'm hoping to keep British South Africa at the least). The biggest change is Greece's fortunes in gaining
Northern Epirus and Eastern Thrace after the Great War, and British 'sponsorship' leading to an economic investment to keep the Russians at bay and the Ottomans in check. Venizelos wins in 1920, and with remaining British assistance, the Ottomans are forced in the Treaty of Sevres to cede the Aegean coast to Greece, and conduct a population transfer. The Bank of Greece is formed, along with several other economic modernizations, contributing to a high rate of economic participation.
The German Empire still wins the Franco-Prussian War, but its ascension to power came with increasing animosity amongst other powers. Frederick III came to power early, and his son, Kaiser Henry, continued much of his success, however the early arrival of the Great War in 1912 prevented the Germans from mounting a successful war. The entry of the Americans in 1915 sped the war's end in 1917, with the collapse of the monarchy. Henry managed a successful abdication with the release of their African colonies and Alsace-Lorraine, much to the consternation of France, however. Germany became unstable in its new republic, with the rise of the Prussian Soviet Republic in the east, and the threat of fascist parties in the south. It successfully repelled these dangers, and managed to stabilize its currency by the time the depression hit in 1929/30.
Austria became a trouble for the Germans, who fought a war against them with an underpowered military, taking longer than it otherwise should have, but toppled the fascist regime, and with a popular plebescite, integrated Austria into the German state. Czech outrage led their alliance with France, along with Poland, directing the course of WW2.
The US came out of the Great War relatively unscathed, unlike Europe, with Rupert's Land in exchange for a forgiveness of British war debts, seen as a money sink in Britain, but a deal for the Americans. The division of the new territory occupied much of the decade for the Americans, with land speculation and resource exploration focusing their attention. A number of immigrants from war-torn Europe poured into these areas escaping the ruins of their old countries. Land speculation and several other factors contributed to a crash in 1929 that spread throughout the world. France, which had the Croix-de-Feu far-right party, along with several other parties, fell under the sway of more extreme positions, believing in a 'back-stab' by Britain and America, allowing the coup on February 4 to enable their alliance to seize power. A different world war emerges, with Germany being the occupied power by France, and the Axis and Allies changed. Greece remains neutral in the conflict, however, and emerges from the war relatively unscathed. Germany rebuilds with allied help, as does a defeated France. Eastern Europe falls under an iron curtain, with the USSR installing puppet regimes into territories it took, and the failure of General Eisenhower to take Warsaw, instead stopping in eastern Germany.
This alternate world emerges by 2012:
USA: from the Sonoran desert north to the Arctic, having also purchased Greenland in 1948 from Denmark, along with Cuba, Bahamas, Bermuda, Peurto Rico, and the Virgin Islands
UK: Malta, Minorca, Hong Kong, Gibraltar (including Spanish Morocco), and former colonies in South America, South Africa, Australia, and New Zealand in commonwealth with them. This UK did not abdicate its world role, rather it eased out of Africa by developing it and industrializing it, in contrast to France's sudden departure in the 50's. The standard of living in former British African colonies is roughly equal to that in poorer areas of the US, UK, or Germany, with stable government, paved roads, stable electric power and sewage systems, rule of law, and widespread cultural ties to the United Kingdom to the point that these countries do not have the endemic problems of our timeline.
Italy: Corsica, Savoy, Nice, Trieste, and Tunis are integrated.
Germany: German Empire, Austria, Pressburg, Sudeten territory, Tientsin, German Samoa, New Pommern, New Mecklenburg, Kiautschou; still ruled under the Weimar Constitution with a President and Chancellor.
Poland: same as second Polish Republic minus any territory in Germany.
Czech Republic: Same territory minus Sudeten region.
Greece: Greece, Cyprus, Crete, Megali territory.
Armenia: Wilsonian Armenia
This is a rough and short version, so it's intentionally leaving out details. My purpose in posting is to ask how to get the timeline to evolve in such a manner in the most plausible path. The areas of concern I have would be how to evolve Britain, France, Germany, Greece, Italy, Russia, and Poland in this timeline. I'm most familiar with American, German, and British history, while the other countries I'm less familiar. The intent is that in this alternate 2012, the United Kingdom is not the withdrawn socialist country, but is instead a robust, vibrant world leader alongside the United States, which is also economically and culturally robust, not suffering a fiscal crisis, and Germany is also a world scientific and economic powerhouse, having redeemed itself during the second world war in its alliance with the US and UK. British South America and South Africa would be independent and prosperous along the lines of Australia and New Zealand, in commonwealth with the UK. That said, if anyone has some ideas on how to fill this rough outline with respect to those areas of concern I would greatly appreciate.