Here in Pittsburgh, we have lots of "Let's go Steelers!" (and some diehards who also say "Let's go Bucs!", but they're dying out). What does that phrase even imply? I assume it's similar to "Go Steelers", which I'm also not sure of the implications. "Go Steelers... to victory!" is a very strange way to phrase the sentence. Does anyone know where this phrase comes from?
Usually, "Let's go [team name]!" is used for teams with two syllables in their names and "Go [team name]!" for teams with just the one. They are used to encourage the team to move and go for it, I suppose.
However, the song did not become famous until 2005.
I expect that the "Let's go [team name]" cheer and other variants came about after the cheer-and-clap from the song by The Routers became popular.