IANAL but I think the constitution only applies to people under the jurisdiction of the US, i.e. in US sovereign territory.

They talk of "U.S. persons", not U.S. citizens: https://en.wikipedia.org/wiki/United_States_person

The government argues (and many lawyers agree) that 3rd party business records are not covered by the 4th amendment and reading them is not a "search." The amendment is very clear on the government's authority to come into your house and look around, and while it seems like it should protect electronic communication, it doesn't (necessarily).

It's actually the Wiretap Act that protects telephone calls, not the 4th amendment. But there's no real analogue of the Wiretap Act for things like email and Facebook.

A US non-citizen person is still different from an alien.... consider children.