This is perhaps just demonstrating my own biases and ignorance, but it seems that most classical composers of renown, with a few exceptions, come from Italy, Germany, France and Austria (and Russia come the 19th century, but the reasons for that are far clearer). So why do other areas in Western Europe- Iberia, Britain, Scandinavia- seem so under-represented?
There's always room for more answers, but in the AskHistorians FAQ on music, there's some fascinating /u/nmitchell076 answers about similar topics to your question: