Most powerful nation on Earth by timeline?

[Lord Halifax]

1519-1648: Habsburgs
1648-1763: France
1763-1914: UK
1914-present: US

It's really not possible to do it for the whole world prior to the 16th century. It could be interesting to do it by region but that's another thread.

1914 doesn't seem like a logical cut-off point for  British dominance, logically the point must be further into WW1 when the Empire's fiscal basis had been weakened and the US had built up its military. I've always thought 1917 makes the most sense, but you can make a case for 1918.