So rather than the NSA hoovering up US phone call content, which they almost certainly have the capability of doing, they just let the UK do it for them?
https://en.wikipedia.org/wiki/Wiretapping#United_States
Otherwise, telecom companies keep records of all calls that take place on their network - the phone numbers, time, duration, etc.
Perhaps not explicitly legal but calls are monitored all the time after switch upgrades. We even applied US specific patches that disable the operator override tone that lets you know someone is on the call. I had to do this after every switch upgrade. One time that specific patch flubbed in a non obvious way and when I jumped onto a random call the people said, "Is someone there? Who is on our call?" and I disconnected.
For what it's worth, my boss had an arrangement with the three letter agencies to give them unfettered access to all the switches and we would even enable non-logging test mode to prevent any of their commands from being logged. My boss and most of his direct reports were not US citizens and one of them openly hated Americans so they did not really care. This was a couple decades ago so maybe by now everybody follows the spirit of the law.
The phone company can't listen to your phone calls and there is definitely no public expectation or journalists demanding that AT&T and others do something about preventing crimes that used a phone by recording all calls and passing them through a Crime Detector (TM).