An alternate means to my Blue Alert timeline.
Basically, time travel alters the outcome of the War of 1812, resulting in an American victory rather than a stalemate. The end result is Britain is stripped of it's Canadian colonies, which eventually become several U.S. States.
Britain, having lost the largest and most profitable of it's colonies in the Americas, later decided to part with all of it's New World colonies to save itself the financial/military burden for a large sum of money from the United States.
The net result of this was the USA becoming a regional power far quicker than in reality, while the infusion of more liberal - and white - individuals from Canada also helped convince the USA to occupy the rich north of Mexico in later conflicts.
Furthermore, Britain benefited from the loss of Canada, as it devoted it's full time to establishing more power on the route to India, mainly gaining the large Eritrea-Djibouti-Somaliland strip.
With the eruption of the Great War in 1914, the Central Powers of Germany, Italy, Austria-Hungary and the Ottoman Empire fought against the Russian Empire, France and Britain. The United States stayed neutral, but the opportunity of expanding it's territories across the world by attacking the Allies was simply too great to pass up. America entered the war on the Central Powers' side in 1916.
The Americans arrived in time to occupy most of Western France. They soon found out that the Germans intended to cut them out of a satisfactory amount of gains, due to the late American entry into the main war effort of the European theater. Accordingly, the American government soon gave a lucrative offer to Britain: in exchange for backing American conquest of all of German Africa, in addition to Spain and Portugal's colonies in Africa, the United States would switch sides. Britain took the offer, knowing that while it could hold it's island fortress for quite a while, it would need outside assistance to liberate the continent.
The war raged on until 1921. The Central Powers were crushed and enormously partitioned. The United States secured lots of property in France in the peace deal. Meanwhile, Europe began to form a league of nations to try and prevent another Great War, the European Union. As part of the United States's 14 Points, there was the principle that countries should be erected according to how much territory could be effectively occupied, not on silly principles of nationalism.
In the 1920s and 1930s, the demagogue Adolf Hitler with his NSDAP looked set to govern Germany, which was in turmoil. However, Hitler and much of the NSDAP leadership were murdered before they could make any real gains, and with a mix of coercive and revolutionary activities, the Socialist Parties of Germany took power in 1933, sponsored by the Soviet Union. By this time, Bohemia and Poland, both established in the wake of the Central Powers' defeat, were also under Soviet influence.
Josef Stalin became ambitious in the 1950s, when without any real opponents - the Empires of the world were slowly decolonizing - he launched an invasion of Europe, seeking to subjugate the whole continent to Communism.
Stalin's offensive was successful, and much of the continent was his within months thanks to blitzkrieg tactics developed by his German allies. Unfortunately for Stalin, the United States was prepared to protect the European Union - which had aligned with the USA under the North Atlantic Treaty Organization - against Stalin's Warsaw Pact.
In a costly war, the Soviets were eventually crushed. Not wanting any more European Wars, it was decided to strengthen the EU at Russia's expense. The large Kingdoms of Sweden, Lithuania, and Ukraine were carved out of Russia, while Russia itself snapped into a population-rich European segment and a resource-rich Asian segment. The Japanese Empire - now known as the Empire of the Rising Sun - had also been opportunistic, having seized much of Eastern Russia.
Seeing the vulnerability of American interests in Europe, the United States - which now occupied much of Europe in coordination with local militias and British forces - began to withdraw westwards, establishing new democratic states.
...Until it reached France. A pro-American regime was installed, with the American President offering the statement, "Being the fathers of modern republicanism, France and the United States are perpetually linked..."
By the '70s, the alliances of the world had stretched, while the Empire of the Rising Sun had also expanded it's reach at local countries' expense. When the United States and France launched a sudden attack on Europe from all sides, nearly every country in the world chose to side with the EU or the United States, initiating World War III, which would be the most devestating conflict in human history...