There's a bit more to it than that. Initially, transatlantic calls were over radio links. Then, in 1957 (IIRC) the first cable capable of voice calls was put in service. Next came satellite links, but because of the time it took to go up to the satellite and back, a satellite channel was typically paired with a cable channel, so that in one direction, the call would go through the satellite and through the cable in the other. All this was still analog. What really caused a big shift in telecom was the move to digital, starting in the mid '60s. This allowed cheaper, better quality calls, without all the fussy analog gear.
Incidentally, I started working in the telecom industry in 1972 and have worked with everything from analog, vacuum tube based, voice carriers to voice over IP and lots more in between. I have seen a lot of changes in that time.
I haven't lost my mind. It's around here...somewhere...