Why was UK considered as US most important ally in WW1, WW2 and the Cold War?

The US was the UK's ally, not the other way around.

I'm not sure it was. Canada has always been a closer ally to the USA than the UK. At least, in the 20th century, and today.

Both were joined by filial bonds, as the US derived their initial racial stock from UK & is a firm Anglo-phile country.

most similar? uk wasn't overrun in ww1 or ww2.

Considered by whom?

they are the same communists Muslims Africans and Asians as you see today are the enemy or opponents not Friends colleagues you could say easy to stab in the back if need be isn't that how it is with money