Sorry, I'd rephrase my original statement a little bit for clarity. I didn't mean at all to say that "nowhere is efficient", which in retrospect is one valid way of interpreting my original statement.

It's not that agriculture isn't hyper-efficient in certain locales. It's that it could be more efficient, if its operators cared to invest in making it so. Until demand rises relative to supply (from supply shortages), there isn't a price pressure to innovate on efficiency. This doesn't stop the "big farms" from innovating, because "big farm crops" are a race-to-the-bottom commodity business. That's why we get more corn, soy beans, whatever every year.

This is all without mentioning the places where agriculture is rather undeveloped, compared to the places you mention (many locales in Africa, central Asia, even the United States and Canada).