Egypt is a mess, but what should the USofA do about it?
A better question would be, what can the USofA do about it?
I suspect the answer to both questions is, nothing. I suppose we could, shall we say, postpone our planned joint military exercises with the Egyptian army. We could call a coup a coup, and discontinue military aid. Whatever we do, though, we lose.
There is a perception in the Muslim world that the USofA might even have had a hand in instigating the coup, and who knows? — that perception might be right. It's always been easier for us to deal with autocrats and military dictatorships than with the messiness of emerging democracies. Kings and Shahs and Generalissimos are better for business.
Anyway, I'm sure we'll "support" whoever comes out on top, although it's likely to take a while before we find out just who that will be.