For clarification, this is completely true of the US, without needing to speculate, thanks to a combination of FISA 702, the ECPA, CALEA, EO 12333, and the CLOUD act. It all has legal footing in the States.

However, it's not at all the reality of a vast swath of other countries (or, at least, not yet; see Chat Control v2). The US is particularly foul (and effective) when it comes to this practice, but anything outside of US jurisdiction that doesn't have an office in the US can't be touched by laws like these, and the laws of most other countries tend to be significantly less invasive than American ones when it comes to data interception and the practices surrounding it.