OK, so "everything" is a bit of an exaggeration. Just the most important thing. Probably the most powerful enduring myth about FDR was that his New Deal brought the US out of the Great Depression.
Why is this so important for us now? Because many policymakers today believe the myth, and their actions today can have similar consequences on the American economy.
Here professor of history Burt Folsom expertly explains how, and when, the United States got out of the Great Depression.