There won’t be a US or Australia or for that matter New Zealand left by then. The English speaking world will have the state of New York, the state of Chicago, the states of London, Edinburgh, Sydney, Christchurch etc. But yes, I don’t see why will be any English-speaking nation state left by the time my toddler nephew is in his last years, if Scotland does become independent after the referendum next year. And before you cheer for all the technology advances, have a read at Italy during the Middle Ages. Constant wars, strifes, shifting alliances, France and Germany and Russia meddling and interfering and often being invited by some alliances of English-speaking City States against another alliance.
And oh, BTW yes, the English-speaking world will produce many 21st century machiavellis.
The best alternative without war would be all the micro states have becom confederations so you get little Switzerlands. Rich, inventive and self governing, but can hardly even control it’s own destiny on the international and are on the fringe in geopolitics.
I still stand by my assertions that significant nation states from cultures not subject to local separatism ideology, such as France and Germany, will be able to exert the most influence out wards, and pick up leadership of the West by default just because they will be the “biggest dogs” left after the Anglo-Saxon world decided to commit national suicide by dividing it’s four of existence.
Just like during the 8th century when Charlemagne as the King of Frank.