I understand that it's US and per law, but "no reasonable expectation of privacy" is more of a judgement. It should always mention that it's due to the law.
The statement probably is entirely reasonable if you're born in the US (as you're used to it). Other countries have other expectations of what's reasonable and normal.
The often repeated "no reasonable expectation of privacy" in a public place to me is entirely odd. It's also something that could change (whether such a change/perception is in e.g. NL or in the US).
Technology makes things possible that weren't possible before at all. Meaning, you can store camera recordings for a ridiculously long time. From my buildings security (again: NL) I understood that legally they cannot store such recordings over 28 days. Above that things become difficult (possible but quite a hassle).
In the past people could see what you're doing in a public space. But nowadays you can easily be recorded and that recording could be stored forever. That was never the case before.
As a result, things such as "no reasonable expectation of privacy" should change with the changed circumstances, IMO.