> Maybe there are laws preventing legal access to message content?

Well sure. A lot of laws require a court order. In the U.S. that's usually not too difficult.

It helps Telegram is HQ'd in the UK and the operational center is in Dubai.

Does it? UK and Dubai are USA partners in Intelligence gathering and work together several times.

Biggest example as of late: https://www.bbc.com/news/world-middle-east-58558690