They have always been allies...
The U.S. got involved because Britain was being attacked by the Central Powers (enemies) and Britain is allies with the U.S..
Over the centuries, most western European countries have been allies and enemies (at different times, of course!) of Britain. The US is perhaps the largest ally of the UK.
i think the allies at the end of the war were Great Britain, US. and the USSR
allies war of 1812
Difference in ideologies. (Communism vs. Capitalism)
Major allies were Great Britain and France. Major enemies were the Soviet Union and the People's Republic of China.
Britain, Spain, and France were potential enemies.
The French teamed with the US because they were enemies with Britain.
Germany, Italy, Japan
Britain, Spain, and France were potential enemies.
NVA/VC vs US/allies
Britain in ww2