My initial reaction is to say there should be another member, yet there are several ways to go with this, mostly because we're not yet sure whether or not the team is turning face.
Just think about how pro wrestling has changed over the years.....long ago, can you imagine a team of patriots being booed by the fans? Sergeant Slaughter truly altered the landscape of heel/face dealings, whether we realize it or not. ("Drop and give me fifty, maggot!")
But in the case of the Real Americans, they certainly brought it off, didn't they? Zeb Colter has the type of presence that would allow him to be the mouthpiece for one performer.....or an entire troop of them.
One might say that Zeb leading Jack Swagger into battle is enough. My problem with it is Jack's utter lack of presence on the mic. He's a terrific wrestler, yes, but I feel the team would be better served with a guy who has some personality. In that regard, Big E would totally be the wrong choice; he can't speak any better than Swagger.....plus, E's patriotism showed itself only in response to Rusev and Lana's display of anti-Americanism. For the Bulgarian, Big E is only a small step on his march up the WWE ladder. There are much bigger things ahead for Rusev than Big E. In that way, having Big E as a Real American would provide minimal impact.
If the Real Americans remain heel, there are probably many bad guys on the roster might suffice as a member. But as things stand, Zeb Colter should have more human ammunition on his side.