The part doesn't make a lot of sense, and it's nothing like [what Sousa wrote](https://imslp.org/wiki/The_Free-Lance_(march)_(Sousa%2C_John_Philip)). It's only a march and you can very probably get away with playing it something like Sousa's original (listen to the way the US Marine Band play it). You just need to make sure you put the accents in the right places and stop playing at the correct times.