Here is my opinion... The biggest difference I have noticed when going to games here in america (NHL/NFL) is that is more momentum based whereas some european games it is constant they just change up the chant. With that said I have also gone to MLS games and it is very similar in the manner that the ultra groups stand/bounce and chant/drum the entire time of the game. I think this is just how soccer fans are and the fact of the matter is that MLS is not as big here as the other dominant sports in america. Maybe start by talking to the team or facility to see if the "ultras" can get a designated area so that it is predictable that the section will always be the loud section.

With that said, I support my childhood team which is Napoli as well as my local team DC United. The roar of the crowd you hear at a Napoli game can't even be compared to anything I have ever experienced in my life and it truly just monumental. The DC United games are awesome too but I feel like I had a different experience once I sat on the opposite side of the supporter groups. When I sat/stood near the supporters at the DC United game I very much felt similar energy as I did at the Napoli games except the biggest difference is the magnitude. You can't start that type of magnitude until you "start". So buy a drum and drum away while chanting the whole time. You may get weird looks at first but as people notice that you can actually make a difference in the momentum of a game people will slowly join in.

Same thing happens at NFL/NHL games. NHL is notorious for using the air horns to start the LET'S GO _______ chants, but I have also experience people just continuously yell it and other people will join in. I have never seen another fan tell another fan to shut up because they were chanting LETSSSSS GOOOOOO ________. if you are rooting for the home team.

One thing I would suggest is that your chants involve some sort of clapping throughtout with some rhythm, as some people may not yell but will definitely join in for the clapping... This is how my wife and kids join in during DC United games, as I chant and clap along. This makes it easier for people that may not know the words of the chants or may not even want to yell at all but allows them to easily follow along with the drum or whatever.

Also, remember it isn't just chants but also big ginourmous flags or using team scarfs to hold up. I always love seeing a bunch of people holding up team scarfs or using them to twirl them around too.