What kind of bicycle culture are you looking for? Cycling for transportation is decent in Belgium, but not everywhere. It's mainly Flanders, Ghent is probably their best cycling city, and imo is their best city to visit anyway.
Really special is their culture towards road cycling, cyclecross and track. Thousands of them will go out into gloomy and rainy januari cold to get a glimpse of the Belgian boys beaten in the mud by the same Dutchman over and over again and applaud him over and over again. Of course they care and would prefer a Belgian to win for a change, or any change in who wins, but first and foremost they keep admiring the performance. The same for road cycling, Sagan is incredibly popular there for the cyclist he is, his nationality is secondary. That's not because they're not chauvinistic, it's because of their deep and genuine love for the sport.