What would it look like?

Well this isn't the 1930s.  Different number of farmers as a proportion of the population, to start.  Different number of production laborers, but, not so oddly, a LOT more production.  But a lot more reliance on inventory supply from far afield.

So if some event doesn't look like 1933, lets hope it doesn't look like Syria, 2013.  Or the Balkans in 1995.  Here.  Over a big portion of the USA.

And it can't.  Large areas of the continent would remain untouched by direct destruction and just have shortages. 

Yeah, it's an ugly hole to speculate down.