[Beretta_Vexee]

Perhaps you should limit it to capital cities or states with a certain population size. Including all the European microstates does not seem appropriate to me; Andorra, Monaco, San Marino and the Vatican have very varying degrees of independence and geopolitical significance.

[zamadatix]

Regardless of how one selects states there will always be comments saying it was done wrong. Don't fall into this trap, just stick with one of the UN lists as has already been done here (looks like members+recognized observer states) and accept not everyone can be perfectly pleased with what is considered a state or not.

Interactive data filters would definitely be fun on its own account though. E.g. the population slider or by having a button making it the largest cities above x population instead of countries/capitals or so on with centers of states. It looks like there are several different maps on this site, such things may make it more a single experience with more overall value than the separated parts. Still cool as it is though :) just one possibility to go further with it.