According to my fellow Fool Daniel Kline, the NFL has the potential to "become a worldwide event," and maybe even topple soccer for international supremacy in the distant future. With U.S. dominance under its belt and a desire to expand, it theoretically can ... but I don't think it ever will. The world still belongs to the other version of football, and that won't change anytime soon.

The sheer size of it all
No matter what you call it, soccer is the most popular sport in the world. With over 3 billion followers, its fanbase dwarfs American football seven times over. Soccer is the most watched sport in nearly 60 countries, from Brazil to Uganda, while American football, meanwhile, is the most popular in only one country: the U.S.

Some claim that a history spanning more than two millennia is the reason the planet overwhelmingly prefers the action on the pitch. Others believe soccer's the top sport because with more than 2,000 professional franchises in the world, there's a team for everyone to cheer for, regardless of geography, preference of style of play, or even just the look of the jerseys. 

To me, it's about how accessible the sport is for the average child, whether they're in Manchester or Rio de Janeiro. Soccer requires less initial investment than almost any other sport. According to estimates, an amateur, pre-college career in American football can cost thousands of dollars for camps, equipment, and training.

Soccer, on the other hand, requires a $5 to $10 ball, an empty field, and objects to represent both goals.

Image via Patrick Furlong, Flickr.

The lack of gear required to play removes barriers to entry for millions, and may explain soccer's global presence. American football, meanwhile, is centered almost entirely among the world's most affluent.

Another major advantage
Any argument calling for American football to eventually overtake soccer ignores one thing: the NFL is the sport's sole flag-bearer.

A future where it surpasses soccer as the world's most popular sport will ultimately rely on the abilities of one league. Although it does generate over $9 billion in revenue each year, multi-million-dollar concussion litigation is a major risk, one that could derail, or at least delay, the NFL's international expansion.

Soccer doesn't face the same problem. It has two billion-dollar leagues in Europe alone -- Spain's La Liga and the English Premier League -- with the latter making almost $3 billion in annual revenue, according to Deloitte. In total, European leagues generate nearly $1 billion more per year than the NFL, with untold millions in additional funds coming from South America, Africa, and Asia. America's MLS also makes $250 million to $300 million in annual revenue, meaning that on the whole, soccer is a larger business than the NFL, and it has significantly more revenue diversification.

Why is this important? Imagine if La Liga or Italy's Serie A ever has financial trouble. Even in a worst-case scenario, bankruptcy of a major soccer league won't kill the sport. On the other hand, the existence of American football on a professional level, at least for the foreseeable future, is entirely tied to the NFL.

The final piece of the puzzle
But there's one more thing soccer has that football doesn't: a global contest that commands the world's attention.

The 2010 FIFA World Cup. Image via Jimmy Baikovicius, Flickr.

Once every four years, the FIFA World Cup gives soccer a playoff format on a scale that simply doesn't exist in the NFL. The contest's final has historically been the most watched sporting event on TV, above the Olympics, and yes, the Super Bowl.

In 2006, for example, each World Cup match drew more than 250 million viewers, and over 600 million watched the Italy/France final. The 2014 Super Bowl, which was widely touted as America's "most-watched TV event," generated 111.5 million viewers. Paltry in comparison.

A modern day World Cup generates at least $1 billion in merchandise sales, and when sponsorships and broadcast rights are included, FIFA makes roughly three to four times that in revenue each event. The 2014 World Cup in Brazil is projected to make soccer's governing body $4 billion, with profits of at least $400 million. The NFL's Super Bowl take is typically much less.

The blueprint
More important than the money, though, is the global exposure the World Cup gives soccer. Until American football can establish a similarly themed contest, the sport won't be close to becoming the world's favorite. Before that, the NFL needs to address a couple of things.

First, barriers to entry that make the sport so expensive to play must be lowered. Like soccer, American football must find a way to be accessible for all children, no matter their background -- free handouts of helmets and pads is a start. 

Equally as important, the NFL cannot rely on one league to hold the keys to the future. Soccer, with its multitude of leagues in Europe, South America, and nearly every major continent, has created a good blueprint to follow.

If "Football Sundays" are ever to become a worldwide event, the NFL needs to tackle both of these issues. With that all but a pipe dream at the moment, I don't expect it to happen in my lifetime.

For the other side to this argument, read why Fool colleague Dan Kline thinks "the other football" will take the lead.