The Gilder Lehrmann Institute for American History has an excellent podcast with guest lectures about American history in the widest sense. The latest in this series was a lecture about the history of the cold war by John Lewis Gaddis.
I would have expected Gaddis to start in 1945. He eventually makes clear how the cold war indeed starts around that date. However, he makes a point in asking why did it take so long for these two superpowers to eventually wind up in this duality. He notes that by the end of the first world war, basically it is clear that the US and the USSR are the only real great powers left. He suggests one can even go back further and points out that it was already noted at the time. In the nineteenth century the US and Russia were the only great industrialized nations that were rapidly expanding into an ever moving frontier towards a size that extended way beyond the great powers of the time, France and Britain among others.
Hence it was bound to happen and he introduces us to George Kennan (the first, before George Frost Kennan) who marked this evolving reality. And so, already by 1917 the US were eying Russia and after the revolution, the USSR. The US were also weary entering the Great War, feeling that it was not in their interest to 'save the British Empire'. Inevitably, though opposed to the idea of Empire, the US became one. And so did the USSR and Hitler gambled on the polarity between the two. Yet they teamed up to bring the Third Reich down and only then the true duality came to dominate the world. Until 1989.
More Gilder Lehrmann:
A plea for integrated historiography (Thomas Bender),
The Cuban Missile Crisis (Sergei Khrushchev),
African American generations (Ira Berlin),
Theodore Roosevelt (Patrica O'Toole),
Slave Culture (Philip Morgan).