Is it permissible to eat chicken or meat that does not bear the "halal" stamp in a European country where halal meat is not available at all?

The basic ruling is that the slaughtered animals of the People of the Book are permissible. However, if the meat is not slaughtered according to Islamic law, it is not permissible to eat it because it is carrion, and Allah has forbidden carrion in His statement: "Forbidden to you are carrion." One can substitute meat with fish and the like.