Well for that matter, "Ireland" is not a single country either - but in Cricket and Rugby the Republic and Northern Ireland play as a united team. If you know anything about cricket, you know that the West Indies are a test cricket "nation".
As much as I am not a fan of cricket, despite growing up in Zimbabwe, it was a really great quiz. The only two I didn't get were the West Indies (I was trying Jamaica and Barbados knowing that they play cricket, I didn't think to expand) and Afghanistan.
Which reminds me...can't wait for the "Buzkashi Countries" quiz!
Nations and Territories that make up the West Indies Cricket Team
Hopefully this will satisfy any nitpickers out there!