I remember hearing that American service members are by far the best fed of all countries since WWII.

Along with resource richness, I think it's important to note how USA's geography also makes it extraordinarily safe from invasion. It is flanked by two oceans with die hard allies as neighbors to the North and South. Anyone that wants to invade USA would have to make an impossible amphibious landing or super-blitz through Canada or Mexico. Both of those options are nearly impossible. The entire world vs North America might not even he able to pull that off. Then, once the invaders get to the continental USA, they would have to deal the most possibly armed insurgency due to the culture's obsession with firearms. So, the only way the USA could be militarily taken over is by near complete destruction of its population via long-range missiles. This disregards the USA's vastly superior military power. The USA has more aircraft carriers than the next 7 countries combined and each one is technologically superior as well.

With that in mind, the USA didn't have to direct considerable economic efforts to protecting its homeland, while knowing that it's economic production would go mostly unharmed. In contrast, the Soviet's were scorching their own production centers just so the enemy wouldn't acquire them.

Additionally, the USA has the most expansive freight rail system and the Mississippi River allows for easy and efficient shipping of resources, especially from the food production area (eg the Bread Basket). So not only can the USA produce lots of food without having to worry much about protecting that, but it can also easily transport the food to other locations efficiently. When it comes to food and defense, the USA is overpowered af.