Is it permissible to eat frozen and refrigerated meats available in America while ignorant of the method of slaughter and the one who slaughtered it?

If the region is inhabited exclusively by People of the Book, then their slaughtered meat is permissible unless it is known to have been slaughtered in an unlawful manner, due to the Almighty's saying: "This day [all] good foods have been made lawful for you. And the food of those who were given the Scripture is lawful for you and your food is lawful for them." However, if they are mixed with other disbelievers, or if it is known that they slaughter in an unlawful manner, such as by strangulation or stunning, then it is not permissible to eat from it, due to the Almighty's saying: "Prohibited to you are dead animals, blood, the flesh of swine, and that which has been dedicated to other than Allah, and [animals] strangled or beaten to death or from a [high] fall or by [the goring of] a horn, and those from which a wild animal has eaten, except what you [are able to] slaughter [before its death]."