It is cultural, it is generational, it has way too many variables to type up in a message board post. I agree that part of it is a reflection of this nation. But there is more to it.
In no certain order I blame the trickle-down philosphies of big time college sports creeping into HS athletics, the video game culture; both in the lack of enthusiasm to engage in recreational activity as a whole and a Madden generation that thinks football is just all about mashing the right combination of buttons or knowing a "cheat code", central air conditioning, the demise of farming as a way of life, year round sports teams with no allegiance to a school, school policies or administrations that aren't interested in kids expressing themselves positively, Little Johnny has got to get that D1scholly parents, it can seem endless.
On a personal level, I noted last year that my kid's JV team, while not lacking interest or caring, doesn't seemed consumed with winning. I don't mean a win at all costs attitude but in the moment, when a game is in the balance, there didn't seem to be enough emotion, at least from what I recall from my era of the late 70's to early 80's.
In the end though, it is the kids out on the field that have to make it or break it. We can lament for the "good ole days" but 30 years from now they will be saying the same things we are saying now, I bet.
The thing that I think will kill this sport before concussions is behavior. Look at the stories about parent behavior at youth games, referees being attacked by players, and the latest one where a HC was ejected for unsportsmanlike behavior and he and his staff turned aggressive to the opposing team and even the cops. That's a mighty big ego when you become so emotional that you think you can take on men with guns, tasers, and pepper spray.