FDR didn't take office until 1933, the Great Depression began in 1929. What's more the Smoot Hawley tariff didn't go into effect until Jun - 1930 long after the Great Depression was well under way.
Going into the Great Depression, imports were 4% of GNP, and exports were 5% of GNP. There is no way international trade caused the Great depression, a drop in GNP of 40%. The trade numbers are simply not big enough. (There was an international banking scare that did affect the U.S. market and helped generate the Great Depression, but that's an entirely different issue than Tariffs and trade.)
Now imports are 16% of GNP. And unemployment is 25%.
You’re right about the things I identified as having not caused the Great Depression. I never said they did. They extended, as opposed to having starting, the depression. Just as what you are proposing would extend the depression that began under Bush.