"Our Mann in America" is a weekly column discussing the big talking points in the U.S. for an international audience. Jonathan Mann is an anchor for CNN International and the host of Political Mann.
(CNN) -- The spectacle of big bodies crashing with brutal force has helped make American Football a billion-dollar industry and the country's favorite sport. But the game is changing because its players are being crippled with the whole country watching.
"We do love the big hits," football injury expert Chris Nowinksi told me this week. But, he said "we can't have (former) players all coming down with dementia because we thought it was fun to see them knocked out."
This past weekend, several particularly startling and dangerous collisions broadcast live on television suddenly reminded the country what happens when grown men get paid millions of dollars to grind each other into the ground.
Fans don't normally dwell on that aspect of the action. An American football field is a place of choreography and chaos, astonishingly agile running and players who pluck seemingly impossible passes out of the air.
Americans watch football on the country's biggest religious and civic holidays - Christmas, Thanksgiving and New Years. They make its annual championship, the Super Bowl, the highest-rated program on TV. The world may think of baseball as the quintessentially American sport, but pollsters say this country prefers football by a margin of four to one.
And the U.S. isn't just feeding itself football, it's gorging on the game. During the season that stretches from early autumn to winter, it's all weekend and more. Every community in the country draws crowds with Friday-night high-school games. College teams play to sold-out stadiums and massive TV audiences on Saturday. The big professional games follow on Sunday and Monday.
It's beyond sport; it's culture. A song celebrating its formative role in the lives of America's young men, "the Boys of Fall," is one of the top hits right now on 'country' radio stations nationwide.
The song's lyrics fondly praise 'knocking heads' as part of the fun. In fact, it's football's biggest problem.
The hulking, exaggerated profile of most uniformed American football players demonstrates just how heavily protected they need to be. Over the years, the people who know the sport say players have been getting bigger, stronger and faster at a pace that protective equipment can't match. Even under helmets as elaborate as anything built for battle, players' brains are getting hit too hard.
Concussions are common and less obvious injuries from repeated blows to the brain are just starting to receive scientific study.
The biggest concern isn't even for professional players. America has many more young people playing the game than pros. One study found that some high school players received more than 1,800 hits to the head during practices and games in a single season. The 'boys of fall' really are 'knocking heads' an awful lot.
Rugby players, ironically, don't suffer the same way because they don't wear helmets. They can't hit each others' heads, or hit with their heads, without immediate catastrophic injury.
In football, the hits keep coming because the really profound damage takes years to develop. A recent study of the long-term effect found that NFL players have a much higher risk of brain damage. Even players who hadn't had concussions were still likely to develop it, with symptoms that include memory loss, paranoia and depression.
Some players are taking the medical threat seriously. Dozens have agreed to let scientists dissect their brains after they die, for signs of disease.
Critics say that the National Football League was slow to respond to the problem. They say the NFL even contributed to it by producing and distributing 'highlight films' -- television programming that catalogues colorful and, frequently, dangerous play.
Lately the league is getting more credit, for encouraging new research, for changing its attitude and its rules.
It now says any player who gets a concussion needs a neurologist to allow them back on the field. It has banned helmet-to-helmet collisions.
Even so, there were three of them last weekend, one strong enough to leave both of the players involved unconscious. The video was replayed endlessly on the internet and television because even it startled even fans of the sport.
And so this week the league decided it would do something more: promising to suspend players for flagrantly dangerous hits in the future and imposing unprecedented fines for the ones over the weekend.
Two players will have to pay $50,000 each and a third $75,000. (By comparison, a player who knocked another one unconscious a few weeks ago was fined $15,000.)
That $75,000 fine imposed on linebacker James Harrison prompted him to threaten to quit the game because, he said, doesn't know of any other way to play it.
Harrison has a contract worth more than fifty million dollars, so the threat, like the fine, probably won't amount to much.
But clearly the growing caution cuts against every instinct of the game and some players aren't enthusiastic about it.
"We feel like we're the only gladiators left," said former NFL-er Jamal Anderson. "I like the physicality and the toughness and that's what the NFL is all about. We don't want to take that from the game."
You can bet that millions of Americans who crowd around basement and bar-room TV sets every weekend feel exactly the same way.