Nearly three quarters of a century ago ?
It was Suez (long before I was born) that pushed the UK to Europe. It was clear the US was in no mood to assist the UK to keep it's empire.
Worth remembering that the UKs mantra
We have no eternal allies, and we have no perpetual enemies. Our interests are eternal and perpetual, and those interests it is our duty to follow.
As that has been US policy since (checks notes) 1783