What is the ruling on eating the food of the People of the Book in Western countries nowadays, especially since many foods contain pork or alcohol, and is it obligatory to inquire about the ingredients of food every time one travels to their countries?

A Muslim is not permitted to consume food mixed with alcohol, pork, its fat, or gelatin derived from pork. The basic ruling regarding the slaughtered animals of the People of the Book is that they are permissible, unless they were dedicated to other than Allah or slaughtered in an un-Islamic manner. If it becomes widely known that the slaughter of meats in their markets is not done in an Islamic way, then one must exercise caution and refrain from eating them.