Exports accounted for ~5% of GDP.
Consequences from SH (trade war) eliminated 66% of exports.
There was no domestic demand to take up the slack.
There is a multiplier of 1.2 to 1.8 for every dollar of GDP added to / removed form the economy.
5% of GDP x 66% eliminated = 3.5% GDP destroyed in year 1.
3.5% GPD x 1.2 to 1.8 = 4.2% to 6.3% GDP destroyed by year 3.
Or put another way...
US was a net exporter with collapsing domestic demand, and SH led to the rest of the world refusing to buy American.
Still doesnt explain the growth in the economy during the period from 1934 and beyond...