There are very few people in history that are that pivotal individually. Had Franz Ferdinand not been shot, something else would have sparked WW1. Had Hitler not existed, then someone else would have emerged.

Maybe Churchill was more of a pivot than most, had the UK gone for Hastings after Chamberlain then perhaps the UK would have sued for peace, allowing Germany to fully concentrate on Russia, but it's still a stretch to have Germany ultimately prevailing over Stalin.

Had the US not won independence in 1776 (which is unlikely to be the sole cause of a single person), it would have been gained anyway, just like the other new world colonies from Canada to Brazil.

The conditions that exist are far bigger than one man