The Roman empire didn't do too badly, perhaps not a thousand year magisterium in the West, but 27BC to 476AD is better than the Dritter Reich by a factor of 4000%, or 32dB. And of course it continued in the east to 1453AD- almost one-and-a-half Thousand Year Reichs. Not that it was contributing much for the last 700 years or so.

I think a lot of people are missing an important point with What If history. That is that if any given event A hadn't happened, a whole string of events would have been different. So it's not just no USA to help us out in world wars- the world wars probably would have happened quite differently if at all. Britain could have been the grumbling bitter fascists after defeat by Portugal (so it might have been all the same anyway).

What if Catherine of Aragon had had a son? What if Harold had pushed William into the sea? What if the whole branch had dropped on Isaac Newton's head instead of just one apple? What if Johnny Appleseed had planted marijuana instead of apples?