I used to live in Germany, and my sister is married to a German man. I can tell you most Germans have no earthly clue about American football. That's not a put-down, mind you. I'm only saying that most of them have no understanding of the sport. That said, I did watch some Youtube vids of clips from NFL games with German announcers. I can say the German announcers were excellent. German is my second language, so I can understand them. They knew the game every bit as well as American announcers, and they covered it with excitement and passion. I was thinking if I needed to watch an NFL game in German, it would be no problem. They don't always get American stuff right in Germany, but these announcers certainly did. If the public in Germany understood our brand of football as well as those announcers did, I believe it would be a popular sport there. There are some things American that Germany totally messes up. I saw the original Star Trek dubbed into German and it was awful. That exciting intro that William Shatner did with such passage and drama "Space, the final frontier ..." is atrocious in the German version. It sounds like a Germany university professor giving the same lecture he's given for 20 years and is bored stiff of. But the German NFL announcers were outstanding. They compete with the best American ones, IMO.
Could NFL football become super popular in Germany? I suppose it's possible, but it's a long shot. European football, aka soccer, is king there. Practically everyone there loves it and longs for Germany to win another World Cup. I suspect at best American football could be a loved curiosity in Germany.