Looks pretty much like politicians and therefore propably former presidents to me.
Maybe the enclave controlled u.s government created some sort of Stalin like person-cult surrounding past presidents by integrating sculptures and statues of them everywhere into the major cities ?
Enclave didn't control US government, Enclave WAS the US government, or atleast a "in-case-of" form of it. As with real shadow governments, it didn't take part in politics until it was necessary (in this case, nuclear war).
But don't all US presidents get some sort of statues, that are being stored in White House or Capitol?