There is no England without Rome.
There is no Western Renaissance or Enlightenment without the Arabs.
Can we please end this Angophilic circle jerk?
By that logic, Martin Van Buren was a more significant president than Franklin Roosevelt because he came first and why, the latter would probably never have been born without the former, for a different sperm would have impregnated his mother, and so on.
The literal answer to the question is the American empire. It could easily vanquish all the others put together.
The British empire is very compelling, however, given Britain's role in originating the industrial revolution, establishing its own language as lingua franca, and its geographical reach.
Martin Van Buren's presidency is not necessary for FDR's.
The Roman Empire and Arab Empires are
necessary for the entirety of what we today know as "Western Civilization".
It would be like saying that the fax machine has had more of a impact on the world than the printing press.
Technologically, fax machine is far superior than a printing press: its faster, shinier, and more efficient; however, the printing press is needed for there to be a fax machine.