It could be one factor, but still, the sports action doesn't seem to be organized around clubs even in higher density areas. My country has half the population

It could be one factor, but still, the sports action doesn't seem to be organized around clubs even in higher density areas. My country has half the population density of U.S. and still organizes around local clubs, even in the lowest density areas. Regarding churches and other religious institutions, however, the population density doesn't matter: the U.S. has many more of them, even where population is sparse.