I mentioned regular space travel and alien contact as features of Heinlein's Future History that have not yet materialized in reality. We can add that, if there is to be any alien contact, then it will have to be extra-solar. Neither the humanly habitable Venus nor the easily colonized Mars, let alone the swamp-dwelling Venerians or the contemplative Martians, really exist.
Also, we have neither a world federation nor an imminent religious dictatorship in the United States. A federation is unlikely in the foreseeable future. How about a US religious dictatorship? There are certainly potential First Prophets.
In the Future History, the post-Revolutionary Covenant is followed by social unrest, then by a "mature culture." What would that be like? To a writer like Heinlein, a mature civilization might be based on something like a crisis-free capitalism. However, Marxists argue that crises are inherent in capitalism because competitive re-investment necessarily causes the rate of profit to fall. Such questions will be answered in real political conflicts but science fiction writers can try out some answers in advance.