NATO came about because of WW II not because of any natural affinity between the US and various European countries...
Well let's see, France is the USA's oldest ally
The USA fought alongside France, the UK, Belgium in WWI
The USA fought alongside the UK, France and all the European democracies (plus Canada, New Zealand, Australia) in WWII
The USA fought alongside these democracies in Korea
So yeah, I'd say the USA and the Western European democracies have a long history of mutual co-operation and defense
The USA didn't fight along side France in 1918 and promptly invade it in 1925 for instance.
...Germany and Italy were ENEMIES of US during the war....
Italy was an ally in WWI and for the latter part of WWII
Germany wasn't a democracy during either war...otherwise there would have been no WWI or WWII
...and Russia was an ally back then...
You mean USSR...well I'm not sure too many people in Congress or the Pentagon would describe them as allies during WWII
FDR called the USSR "a dictatorship as absolute as any other dictatorship in the world” after the invasion of Finland
Yet when the USA was forced into WWII, it was recognized that support for the USSR was essential if Nazi Germany was to be defeated.
Basically the USA chose to support the lesser of two evils.
A bit like sending Stinger missiles to the Muj during the Soviet invasion of Afghanistan.
...and the difference between a friend providing military aid and an ally is . . .?
Motivation
The USA gave Stinger missiles to Muslim Afghans not because they were allies but because they wanted them to kill Soviet soldiers. Pay back for the USSR supplying AK-47's to North Vietnam a decade or so earlier.
...half of Vietnam WAS an ally of the USA.
Which half were Americans safe from attack ?