Schneier was very vocal after the Snowden documents on how the NSA has multiple methods to get hold of the data. If it's not via judicial means, it's via extra-judicial means. NSA considers Telegram's servers outside US fair game (i.e. hacking them is not a problem). GCHQ considers servers inside the US fair game. The two agencies exchange intel which allows them to bypass constitutional protections. This is old news.

As for Russia, China, Israel etc. The servers are outside their borders, and mostly they don't give a flying fuck even if it was domestically hosted.