Pregame ceremonies at the Deutsche Bank Park ahead of the NFL game between the Miami Dolphins and ... [+] the Kansas City Chiefs on Sunday, Nov. 5, 2023.By JOHN AFFLECK

FRANKFURT, Germany — A moment early in Sunday’s second NFL regular season game in Germany told me something about how much the American game has soaked in here.

The Miami Dolphins faced a third down and the somewhat pro-Kansas City crowd, this was technically a Chiefs home game, began making noise to disrupt the Fins offense.

Thousands of American fans howled, the way they always do when they want their team to make a big stop. Just as loud, if perhaps a bit more shrill, thousands of German fans immediately joined in — by whistling, a sound that will be familiar to soccer fans and is roughly equivalent to booing.

The thing was, it didn’t feel awkward at all. More like fans of American football cheering with a local accent in packed Deutsche Bank Park.

It turns out that Kansas City’s 21-14 victory over Miami was the fifth major college or NFL game I have attended overseas since 2012. I’ve seen Notre Dame defeat Navy and Penn State edge Central Florida in Dublin, and I watched two NFL games in London in 2017 — Ravens-Jaguars and Saints-Dolphins on consecutive weekends as students from the John Curley Center for Sports Journalism at Penn State filmed a short documentary about European fans of the U.S. game called “Quiet Sundays.” So I’ve got a sense of what these events look like.

Also, to be transparent, I was in Frankfurt at the invitation of a former student — the director of our football doc — who now works for the Chiefs. It was a happy bit of life coming full circle, but it didn’t impact how I felt about getting a fresh look at the development of American football in Europe.

To provide a little background but keep things simple, the colleges and the pros do overseas games for different reasons.

For the colleges, it’s mostly a flex: Look at our program and our institution, it says, which is out in the world doing things. It’s also a chance to get alumni together in Ireland, which has an appeal on its own, particularly for heavily Irish Catholic Notre Dame and Boston College, and is an easy trip for fans who might be a little reluctant to travel outside the United States. Those stadium crowds are mainly American tourists.

For the NFL, games outside the United States are a different story.

To start with, it’s hard to imagine the league being more dominant than it already is at home. Nielsen ratings data found the NFL had 82 of the 100 most-watched programs on American TV in 2022, and all but one of the top 20. The other was President Biden’s State of the Union address.

To expand in the future, the NFL has to — and is — looking abroad.

But in an age of sports globalism, competition is tough. Viewership estimates for the European Champions League final worldwide last spring were around 450 million. After a rift with China over Hong Kong protests in 2019, the NBA’s viewership there bounced back last season.

American football, meanwhile, has some disadvantages on the worldwide stage. Its rules can be difficult for newcomers, and officiating is highly legalistic. I had to wonder what the Europeans thought about the 15 penalties called during Sunday’s game. More importantly, it’s a logistical nightmare to put on games overseas — all the equipment that has to make its way across the ocean because there’s no real football infrastructure in Europe. Then there’s the jet lag.

Nonetheless, the NFL has made regular-season games in London a part of the schedule since 2007 and Mexico City has hosted games a handful of times.

Germany passed its early tests with signs there’s greater interest to mine. As long ago as 2017, when we were making the European football fans documentary, a sports editor suggested that since half the London crowd was German, so the NFL should play games here.

Tickets for Sunday’s sell out in Frankfurt were snapped up in minutes last June, with more than a million requests for just 50,000 seats. And I saw fans lined up for about a block on a chilly Saturday to tour a river boat, sorry, a ChampionSHIP that the Chiefs had docked on the River Main.

The scene outside the stadium prior to the Kansas City-Miami game featured a huge fan fest with mostly Germans, Americans and a smattering of British fans eating tailgate food, having a beer and playing football skill games.

Fans celebrate before the game between the Miami Dolphins and Kansas City Chiefs in Frankfurt, ... [+] Germany, on Sunday, Nov. 5, 2023.By JOHN AFFLECK

It was a good-natured scene, with many European fans doing something they do, which is wear a jersey of any NFL team – even one that isn’t playing. A young man in front of me in the stadium wore a Jaguars jersey and waved a Jets scarf, for instance.

One thing I didn’t see, which I did at Wembley in 2017, was explanations of penalties on the scoreboard.

Seems like, when it comes to American football knowledge, the Germans aren’t just whistling.