Anecdotally, England has a population of 50 million or so and drew an average of 683005 people to Premiership soccer games on any given game week this past season. The USA has a population of around 300 million and they drew an average of roughly 134000 per week (with 2 less games) for the MLS. For American football with much bigger stadiums and far more interest than soccer the TOP twenty teams in the NFL draw an average of 1.1 million fans per weekend, which is nowhere near the 6 times population enjoyed by the USA. My point is that just because a country is larger doesn't mean its attendances should be higher.
I don't see this as a lack of realism at all.
---carefully steps away from enormous can of worms opening up---
Once I scored a basket that still makes me laugh.