Is it permissible to eat chicken and Kentucky Fried Chicken slaughtered in a non-Islamic country, without being certain that it was slaughtered according to Islamic law?

If the majority of a country's inhabitants are from the People of the Book (Jews or Christians), then the general rule is that their slaughtered animals are permissible, unless it is known that the animal was slaughtered in a manner that violates Islamic law or was dedicated to other than Allah. As for the slaughtered animals of disbelievers who are not from the People of the Book, they are forbidden. The permissibility or prohibition of slaughtered animals depends on the method of slaughter and the religion of the slaughterer. It must be noted that the predominant method of slaughter is what matters. So, if it becomes widespread among the People of the Book to take the animal's life by unlawful methods such as stunning or strangulation, then their slaughtered animals are considered carrion and are not permissible to eat.