A nice quote about how football and nationalism come together neatly, from Nations and nationalism since 1780: Programme, Myth, Reality by Eric J. Hobsbawm, p. 143 (emphasis added):
Between the wars, however, international sport became, as George Orwell soon recognized, an expression of national struggle, and sportsmen representing their nation or state, primary expressions of their imagined communities. This was the period when the Tour de France came to be dominated by national teams, when the Mitropa Cup set leading teams of the states of Central Europe against each other, when the World Cup was introduced into world football, and, as 1936 demonstrated, when the Olympic Games unmistakably became occasions for competitive national self-assertion. What has made sport so uniquely effective a medium for inculcating national feelings, at all events for males, is the ease with which even the least political or public individuals can identify with the nation as symbolized by young persons excelling at what practically every man wants, or at one time in life has wanted, to be good at. The imagined community of millions seems more real as a team of eleven named people. The individual, even the one who only cheers, becomes a symbol of his nation himself.