Lane,
I don't believe that. Go to most restaurants and you will find starches on top of starches, a respectable portion of meat coated in more starches, and the occasional sliver of vegetable, not more than a garnish. The recommended five to ten servings of fresh veggies a day per person would take a lot of land, tending, and transportation plus it's time critical. It's cheap and easy to turn out wheat flour and corn meal.
The restaurant will give you what you order. If you order vegetables instead of a potato, that's what they will bring you. The problem is that people don't order the right thing.
As far as the ability of the US to grow, raise - and deliver fresh stuff, I believe in technology and in ability of US businesses to adjust and serve according to demands of consumers. As far as veggies, frozen are nearly as good as fresh, which means one big hurdle is already overcome.
I think the US farmers would welcome demand for higher margin stuff.
OTOH, of the healthier food, as in meat, veggie, fruit categories certainly cost more, which would make things harder on people with tight budgets. OTTH (on the third hand), savings from less medical care needed would probably eventually pay for increased cost of food.
Joe |