US government as a larger entity already can hack into any social media service, a social media service it couldn't hack wouldn't long exist without comming down with continious cyber attacks until it collapses. Proof of this is all the drone strikes of middle eastern and iranian terrorists who definately like the idea of end to end encryption.
As smaller entities, many parts of the US government cannot hack social media. What this means is the NSA and CIA can read your chats, however clever you hide them, but the FBI and Department of Fish and Game cannot. Why? Because CIA and NSA isn't running to a court to prosecute people. They rarely bother with arresting people. You either end up dead or confounded yet again as your masterplot fails like Wiley Coyote.
FBI and lesser agencies who enforce laws for purposes of arrest and prosecution have to submit evidence in a court of law, and defendants have what is called "Discovery". They are allowed to look at evidence, pick through technical aspects, have it objectively, forensically analyzed by a third party who can publish technical details for their defense.
It is why you'll see mostly blurry images of satellites giving a broad view of sites, but hear the CIA did a vein analysis of someone's hand or read a licence plate number. They don't want to give away exactly how precise their capabilities are, just enough to scare the shit out of terrorists, afraid to go near a window for a decade, least they be seen.
Most people don't commit the sort of crime this level of attention brings. If a judge demands the evidence from the CIA or NSA they usually don't respond, or send a clueless generic spokesman who doesn't know how to reply, and at best faces 6 months paid leave in a jailcell for Contempt of Court, literally not knowing the judge's anwsers.
