Unless I'm missing something that doesn't seem to emphasize or strengthen your point in any way. Just because the population of Michigan dwarfs that of Liverpool does not definitively mean Liverpool FC couldn't fill a similar size stadium.
As I said, its just the fact that they attract so much in Michigan, does not mean they would do the same in the UK. These fans in the states have a chance to see their heroes play once, maybe twice a year, so when the oppurtunity arises, they all flock to the game. It does not mean it would happen in the UK too though.