Surely the null hypothesis isn't "The USA would have a domestic industry for every crop known to man if not for external factors"
Or (more likely) they would not have access to many crops at all.
Personally I don't mind not having strawberries in the middle of winter, but for some they care about that.
Let's ignore whether we'll actually get there, that's a very deep question and entirely theoretical for now.
If we could snap our fingers and domestically produce most or all of our own products, would you not prefer that?
Oh that's 100% what Potus thinks.
There's no other rationale for this other than thinking this.