Its not exactly resource wars that the US has fought, we haven't extracted much in way of resources from the countries we have fought in. The wars we fight are specifically about maintaining monetary dominance, if you go against the petrodollar and you don't have nukes then we turn your country into a crater.

So, to the first point people have brought up here, yes, wars can no longer be paid for through printing so less war. Additionally, fewer wars because there is no struggle for dominance over the moneytary system. There's no profit in resource wars, exploitation like this died off hundreds of years ago because the juice isn't worth the squeeze.