Ah, 1984, the supremely effective anti-socialist, anti-communist novel. I, a child of the cold war, did not appreciate how anyone could seriously entertain communism. Having learned a little history, I appreciate the novel more.
There were many times when the Germans came close to forcing French capitulation. Russia and the Central Powers might have patched things up, and we would have seen a reprise of the Holy Alliance. The Holy Alliance, had it remained intact, would have had the power to dominate the world.
I don't doubt the Germans could have conquered the French in WW I--without the British or the US. I don't think they could have rolled the British Army out of France as easily as they did in WW II, and the more successful the Germans were, the more likely the US would be pulled in.
You take this blindly patriotic stance: the US is the most powerful nation, it has always been the most powerful, etc.
Actually, in WW I Britain was more powerful militarily than the US. Germany may have been the best on land and in the air. But I see the German forces being worn down by fighting Russia, UK, France, and the US, just as it happened in history.
The speculation of Russia and Germany uniting again in WW I isn't credible because of the blood ties between the Russian monarchy and the British. There is also the religious difference of Eastern Orthodox versus Lutheren and Catholicism of the central powers. These are powerful popular forces that prevent this alliance.