>The problem is less commercial growing and breeding and more that US consumers have no notion of seasonality, and will happily buy asparagus in September and tomatoes in March.

I mean, in our defense, if we actually ate mostly or only what was in season locally, we would mostly live on squash, beans, bread, and potatoes. Real, tasty vegetables are just plain difficult to grow across much of the country, and shipping from the places with easy growing to the places with difficult growing brings in all the tradeoffs of trucked produce.