Re: There was a time...
This time when all our infrastructure was UK made, and we didn't trust the USA, was this a time when Messrs. Burgess, Maclean, Philby and Blunt were running our intelligence agencies, perhaps?
Everything I've read suggests that the USA, or at least their intelligence agencies, didn't trust us for many years. They thought we were leaking information to the Soviets. They were right, too.
Real life is rarely black-and-white, particularly when it comes to spying.