Soccer will likely have to follow suit.
ETA: And come on, that article has one of the greatest quotes ever:
Ha!
I wonder if the changes required in the NFL would get more at the basic appeal of the game, vs the changes required in the other sports. As Ellis notes, soccer will likely have to adjust as well, though if the impact is more on physical defending rather than headers (as that article and some others I’ve seen suggest), that could also open up the flow of play a bit. Most of the changes in the other sports have been around the edges, though; it seems like the issue with football is the constant crush of bodies on every play.
I’m thinking about the lines hitting each other, the tackling, and the blocking, rather than the big crunching hits. The NFL will continue to make progress against the big htis and kickoff/punt returns, I’m sure, but what if the next round of research indicates even more strongly that it’s the routine stuff that is at the root of the issue? Probably a different thread, but that’s the second wave, decade-or-two out reckoning that I’m kind of worried about as an NFL fan.
I could see a scenario where all of these other sports (soccer included) had made a decade of progress on player safety, right as a new wave of studies came out basically suggesting that tackle football was unworkable. It’s basically the only possibility I can think of where NFL isn’t top-of-the-food-chain for the foreseeable future, and where soccer would have any kind of opening to get to that level in the US. Still think the NBA is probably the winner in that scenario, but it would be interesting to see things shake out.
To the OP’s question: Soccer, is It Catching on with the Young Americans? My answer is Yes, but gradually. I realize I do live in a city that is soon to get an MLS franchise, but plenty of folks I know are aware of Messi, Christiano Ronaldo, Rooney, etc. They may not get any deeper than that, but are aware of some of the bigger names. More people than I was aware of cared about Leicester’s run for the Premier League title.
It helps that soccer is on TV far more often now - MLS on ESPN & FS1, and EPL on NBC, and now Bundesliga on Fox and FS1&2. The World Cup has all the matches televised. The Copa America Centenario will have all its matches televised (which is a pretty big deal when you think about it). It’s not going to explode, but I think the slow and steady groundwork that has been prepared is starting to pay off. They tried to go too big, too fast in the 1970s with the NASL and it fell apart. It also hurt that you didn’t have the cable explosion of today that allows for European leagues to be easily watched as well as the American league.
It also helps that social media is so ubiquitous. It makes soccer fans in the US realize that there are loads of folks just like that. The American Outlaws likely couldn’t have made even close to this sort of membership before the internet.
Time for this thread again?
Lots of evidence soccer interest in the U.S. is indeed growing- check
Standard old-timer excuses to ignore the obvious- check
Great job, everyone! Our work is done. See you next year!
Most of the die hard soccer fans in my circle were born in other countries and are infecting the rest of us by having it play in the background during a memorial day barbecue.
If the “This is how I, as an American sports fan, would change the rules of soccer” thread appears during Euro 2016, instead of just at every World Cup, then we’ll know for sure that soccer is catching on. 
I think it may be likely this year, as the Copa America Centenario is running concurrently with Euro 2016, and the Copa will get a lot of pub in the US since it’s being hosted here and the US team is in it. Someone is bound to start that thread ;).
Although I may be a bit old school in my thinking here, I think soccer will truly have caught on when the big names you need to know aren’t ones playing in a foreign league. It’s sort of like saying baseball will truly catch on in England when they know who Bryce Harper is. That’s not really a thing; baseball will catch on in England when England has a really serious professional baseball league with stars that English people have posters of. (Japan, of course, being the perfect example of a place that actually happened.)
This isn’t to say that European club play doesn’t have its fans here, because it does. I know people who are ardent Liverpool or Man City fans. But most of the action and spent money is in… well, Liverpool and Manchester. That’s where the stadia are, where the action is, where people flock to the games in club kit and cheer and get into arguments over whether Smith is better than Jones was. The same people in the Toronto area who watch Liverpool can’t be arsed to bother with Toronto FC because they perceive, quite correctly, that Toronto FC is a minor league team that would be completely blown out of a second tier European league. MLS play is simply not as good as the best European leagues, and that creates a vicious cycle; if an elite prospect is choosing where to play, soccer’s major leagues - the EPL obviously but you’ve got the Bundesliga, Serie A, La Liga, etc etc - can offer piles of money that MLS franchises cannot. So the stars go there, those leagues remains strong as hell, and MLS remains a backwater with a calibre of play that just isn’t what you see in the top circuits. Many observers will say it’s not one of the world’s ten best leagues.
How, exactly, that gets fixed I honestly don’t know. And it may be harder to reverse than ever because TV viewers can see top notch soccer much easier than used to be the case. Every decent cable provider can get you more EPL games than you can find time to watch now, in brilliant HD.
Now, having said all that, make no mistake; MLS has succeeded. It’s a well established business, anchored by a large number of stable franchises, and it’s not going anywhere.
Eh… I think soccer being very different than any other sport in terms of having multiple high quality leagues means that I don’t think this has to necessarily follow for the sport to catch on. One of the interesting things lately is that a lot of Premier League teams are branching out really, really big into East Asia. It turns out there is a ton of money being spent on merchandise in China, especially. Those people may not know folks in the domestic league (which this past offseason went on a ridiculous spending spree), but I think one can say that soccer has caught on in China.
I think there has to be an adjustment of expectations. American fans are used to watching the “best” in a sport in their domestic leagues (NFL, MLB, NBA) and not having their domestic leagues being of a lesser quality. It’s strange to tell Americans that you have to be like Japanese baseball fans or Dutch soccer fans - who are very passionate about their local teams, but also follow the bigger leagues.
Or I guess one can compare to college football, where a lot of fans support teams that are well below NFL quality.
But I guess there needs to be that feeling of ownership (fan-wise, not money wise :D) of the local team. In some cities that definitely does exist, and the MLS franchises play that up. You can definitely see it in Kansas City, Seattle, Portland, and even in NYC to a point. Atlanta is trying for that sort of mentality as well (which is the only possible reason I can see the horrible “United FC” name to make sense).
By arguably the most important measure - no, soccer is not catching on with the Young Americans (whether they are David Bowie fans or not). Youth participation in team sports in general has been dropping in recent years.
The only team sport with any increase in youth participation since 2009 is ice hockey.
Maybe there are oodles of kiddie soccer pickup games going on out there (obviating the need for parents to shell out $$$ to have their children play organized ball), but I haven’t seen much evidence of that.
I expect pro soccer game attendance and TV ratings to continue to improve (given interest among immigrants), but I don’t see it otherwise catching fire and overtaking football, given that soccer is basically boring as snot to watch, though fun to play.
*gawd, don’t the purists looove their nil-nil ties. 
But by those numbers you could argue that football is going to die soon and no young people will care about it (since it has a small share of participants and is facing double digit declines in participation).
The only sport that has more participants is Basketball. From my own anecdotal experience with two youth soccer clubs, we continue to see growth at all levels, but most of the growth has been at the competitive level even as the ‘rec’ level is starting to flatten out in numbers. My other anecdotal data point is that I was at two different elementary schools in the southeast recently and at recess, at both schools, the main sport being played (really the only sport being played) was soccer. The games looked very competitive, had both genders playing and the kids look very skilled for 1st and 2nd graders…
I do believe though that the participation numbers nationally will continue to decline a little bit for soccer. The fast growth of competitive clubs, increased focus on sport specilization and young start for travel/academy soccer (U8) will turn off casual players for sure.