How to set up realistic international leagues?

[cogitabondo]

I prepared a full scheme of 32 teams in order to set up a European League but I totally lost reality illusion due to the following problem:

Despite of having entered correct country location for every team, when I run the inaugural draft (or fill up teams with fictional players) the nationality of players is based exclusively on the supposed League countryside (which can't be "Europe" or "International", but must be a single country).

So, if for instance I select Italy as league countryside, I have these two possible outputs, both not working:
1. if I set a low foreign players percentage, most players will be Italian.
2. if I set a high foreign players percentage, most players will be North or Latin Americans.

Is there any way to have a Spanish teams filled with a majority of Spanish players, an English team with English players and so on?

Thanks, ciao!