More Words, Deeper Hole

Grain is useless without the infrastructure to convert the stored form into the edible form. (grinding and baking or malting and brewing, generally. Rice is different but not that different.)

This does three things; it concentrates storage, it concentrates power (owning a mill is part of being elevated to nobility in Anglo-Saxon law; way back in the neolithic you use up young female slaves on saddle querns... the point being that having control of the convert-to-food process is a power concentrator), and it gives you a continuous static defense problem. The continuous static defense problem -- even if the field crops are fine, if the mill burns you have a problem -- begets standing armies. Everything else in Eurasian history follows directly from standing armies. (Once you've got the standing armies, you patriarchy, god-king autocracy, field-taxes, et multi-cetera, but it starts with defending the beer and bread supply begetting standing armies.)

Indigenous food production in NorAm was diverse in ways it's difficult to emotionally understand. You would get one cultural group using layered gardening, corn-beans-squash but not as field crops as such (no plow! not plowing deeply offended settler observers), aquatic plants, and tree crops in the same area at the same time. In terms of return for energy input people keep having to roll saving throws against disbelief at the resulting numbers. These cultures were vulnerable to attacks on food storage in early winter but not vulnerable to famine to anything like the same degree Eurasian cultures (with much more concentrated agricultural production) were.

(You can still get nice chestnut flour from Italy. It's not the same stuff as the North American version, and it's never had staple-status the way ~chestnuts (there's a lot of tree specifics involved and since there was an extinction event around 1900 there's a lot of questions) did for the Creek tribes in what is now the US southeast, for example.