Great Britain is the traditional enemy of the United States of America, as they supported the Confederate States of America in The War of Secession. Because of this, the USA sided with Germany during the Great War and World War.
The War of Secession
Great Britain, lead by Prime Minister Palmerston, was eager to regain lost ground from the American Revolutionary War and the War of 1812. When Confederate Ambassadors aboard the Trent were taken by an American Ship, Palmerston issued an ultimatum to the USA, to which Lincoln and Seward were slow to respond. Prince Albert attempted to intervene in the diplomacy surrounding the Trent Affair but was stricken with Typhoid and died in the first weeks of December.
When the CSA won a decisive victory at Bull Run, Palmerston seized upon Napoleon III's offer to recognize the CSA as a sovereign nation.
This lead to a blockade of Northern ports with significant skirmishes between US and UK navies. The Confederacy meanwhile received aid and support and were successful in their campaigns. Palmerston noted in his memoirs his satisfaction at cutting the fangs from the American Leviathan.
The Great War
British superiority on land and sea was at its peak prior to The Great War. Following The Great War, Great Britain was wracked with poverty and incredible inflation because of the reparations exacted by the USA and German Empire.
Interbellum and Great Depression
The draconian war reparations calculated against France, Great Britain, and the CSA by the United States and Germany lead to horrific unemployment prior to the Great Depression, and beyond after the great stock market crashes.
Much of Great Britain's capacity for industry had been destroyed in the final months of the Great War, and lacking the capital, had not been rebuilt. Added to this misery were the attempts by the Chancellor of the Exchequer, Winston Churchill to strengthen the pound in foreign markets, which resulted in further loss on exports, provoking wage decreases leading to the General Strike and Crisis of 1926.
The troubles of the 2 million unemployed were compounded by the losses from the Stock Market crash in 1929. By 1932 when Sir Oswald Mosley created the British Union of Fascists, the party was quick to rise in political power. By the general elections of 1935, the BUF had sufficient clout to secure a majority.
Following his election and posting as Prime Minister, Mosley continued his fascist leanings, encouraging legislation that strengthened Britain, restored jobs, and otherwise built the public trust in the BUF, and by 1938, the BUF was winning most elections around the country.
In November of 1938 a clandestine meeting of Benito Mussolini, François de La Rocque and Mosley forged the Axis of Freedom.
The World War
Beginning in 1937, the BUF government of Great Britain had started construction of war matériel and created stockpiles around the country to be assembled at the outbreak of war, as had been done in France and the Confederate States of America.
Putting aside past differences, Great Britain banded again with France, and instigated The World War, wherein they were heavily crushed, losing Scotland to the Scandinavian Union and Wales and Cornwall to Ireland. The royals were forced to abdicate, and Britain was a weak democracy until the time of the Spasm.
Post-SpasmFollowing the Spasm, the royals were invited back to the throne, with William Arthur Philip Louis Mountbatten-Windsor serving as King, his father, Charles having perished in Moscow with the nuclear attacks.
In 2005, King William was married to Scandinavian Princess Victoria (who is also the heir-apparent), and thus England enters to personal union with the Scandinavian Realm. A growing Unity Party is pushing for full integration into the Scandinavian Union. Brittanic English has begun to be peppered with Scandinavianisms, especially by those who support full union with the Scandinavian Union, as opposed to personal Union.