Thinking more in the sense of being forced to introduce a backdoor, weaken encryption, in the future which would give the US more data. Yes the encryption algorithm is theoretically very secure.

Any entity that operates in the US has to abide by US laws, after all. Probably not a concern for US citizens since they're allowed due process but creates risk for non-Americans looking for a truly secure messenger, especially if they live in a place that is currently at odds with US policy (Canada, Europe).