At least in theory they have to get a warrant, although there are plenty of examples of tech companies handing over information without one. They definitely have access to all the same information if they really want it though.

Edit: In hindsight I think I may have misinterpreted how that post was intended. American government agencies do have a harder time getting access to TikTok's information, although at least for US users TikTok has separate servers that make it possible for them to do so.