Buckwheat is a very useful crop, resulting in healthful food. It was (and is) extremely popular is Eurasia (especially Russia and China).
However, despite the fact that - as per Wiki - it was one of the earliest crops introduced by Europeans to North America, it doesn't seem to have taken here very widely as a crop - USA and Brazil, two biggest growers, each devote less than 1/15th of the cultivated area to it than Russia or China, and yield <1/10th of crop tonnage. Canada 10 times worse. If you scale that up to the whole continent, Americas are even smaller share compared to entire Eurasia.
Aside from the growing stats, buckwheat as food is virtually unknown in USA - the only 2 subcultures that show it are places with many Eastern European immigrants (Polish, Russian and Ukranian, e.g. NYC) and Japanese cuisine, which is of course somewhat new. It didn't seem to have penetrated any further than that, even in multicultural centers like NY.
Is there a specific reason for that through the last 400 years of history?
Climatological concerns (Buckwheat can't grow in too hot a climate)? This seems weird given Canada's low volume. Soil specifics? Relative cost to nutrient ratio vs. other crops? Pollination issues?
Ideally I'm looking for some sort of research, as opposed to WAGging.