Indiana Jones was necessary to the plot

In an episode of Big Bang Theory, Mayim Bialik's character Amy says that in Raiders Of The Lost Ark that Indiana Jones wasn't necessary to the plot since if he hadn't been there the same thing would've happened with the Nazis finding the Ark, opening it, and getting all blown to bits or getting their faces melted off or perishing somehow or another in the process. Well she was wrong, Indy was necessary. Without Indiana Jones the Nazis would not have found Mariam's bar since they followed Indy there. Without finding Mariam's bar they wouldn't get the medallion they needed to find the Ark's hidden location so they would not find the Ark so Indy was essential to the plot.