Several things are likely to have not happened had Indy not been there. For example: The Nazis would not have followed him to Nepal to take the medalion from Mariane. However, given enough time, the Nazis would have eventually found the Ark. Originally though, however, the plan was to fly the Ark to Berlin to be opened for Hitler on a plane that was destroyed by Indy originally. From there, it would have killed Hitler and stopped WW2 from happening. Other events are unpredictable, however, but overall, the Nazis would have still died, making Amy partially right.

[Also, yes I know this thread is years old, but I just wanted to put my theory out there after having watched TBBT and Raiders recently]

Several things are likely to have not happened had Indy not been there. For example: The Nazis would not have followed him to Nepal to take the medallion from Mariane. However, given enough time, the Nazis would have eventually found the Ark. Originally though, however, the plan was to fly the Ark to Berlin to be opened for Hitler on a plane that was destroyed by Indy originally. From there, it would have killed Hitler and stopped WW2 from happening. Other events are unpredictable, however, but overall, the Nazis would have still died, making Amypartially right.