App update for removed countries in google play store An Android app was available in all countries in the playstore.
After a few months, the app was removed from one country ("country XXX")

what will happen if a new version of the app becomes available on the play store : will Google push this new version and update the apps that were downloaded in "country XXX" ?
It won't. You can control distribution in any way you want without changing the application binary, so doesn't make sense that a new updated version will change distribution control.

From https://developer.android.com/distribute/googleplay/developer-console.html#distribution-controls


  You can use controls in the Google Play Developer Console to easily
  manage the geographic distribution of your apps, without any changes
  in your application binary. You can specify which countries and
  territories you want to distribute to, and even which carriers (for
  some countries). When users visit the store, Google Play makes sure
  that they are in one of your targeted countries before downloading
  your app. You can change your country and carrier targeting at any
  time just by saving changes in the Google Play Developer Console.