Is it permissible to apply the terms "lands of disbelief" (bilad al-kufr) and "lands of polytheists" (bilad al-mushrikeen) to Christian countries, despite believing in our Master Jesus (peace be upon him) and the obligation to treat them kindly?

"Whoever desires a religion other than Islam, never will it be accepted from him." Christ Jesus, peace be upon him, was not a polytheist; rather, he called for monotheism. Contemporary Christians have deviated from his call and committed shirk (definition) (associating partners with God). As for showing kindness to disbelievers who are not hostile, it is permissible and does not contradict calling them disbelievers.