If I may hazard a guess, I would suggest that the expression "changed history" likely came from the more plausible and lengthy expression "changed the course of history," which could certainly be the case in a given example (think of the death of Hitler, or any other tyrannical dictator) where had said event not occured, then the course of human history could have been dramatically disparate from factual reality. On the other hand, I wouldn't put it past some dolts to use "changed history" in such a literal and baselessly false manner such as you suggest, but I'd be willing to bet that among more intellectually advanced circles in society, even the wish-washy shorthand version is often used to express the intentional (read: plausible) meaning...

Further reading: http://top-10-list.org/2009/07/15/top10-people-changed-history/

(please excuse any typos... the old computing box is acting rather strangely today)