as we know the European Union is the nearest step that humanity had done to a Political Union, and in that union there are 27 countries that are trying to be one single economy.
but in the past years some countries wanted to be part of this Union, but if you want to be part of it you should have or pass several Rules that they need to know if you could be part of them, like first of all they need your country to be in Europe because is OBVIOUS, is easier to trade between countries that are near each other.
turkey is an example of the countries that wanted to be part of the EU but some of the countries negate the access to this Union because even though in the rules there isn't anything that talks about RELIGION this is the main issue that makes Turkey not part of the EU, and other one is that Turkey is very near some Asiatic countries that they aren't political nor social stable.
so this could cause some wars between come countries that are near Turkey, people want to be in a economical and in a better country, health, and other main ponts can cause people going to Turkey so that is a big reason that other countries like France don't want Turkey part of the EU. people of other parts can enter from there.