Is it permissible to avoid inviting disbelievers in non-Muslim lands to Islam if it is highly probable that they will not embrace it, for fear that they will be held accountable and thus deprived of the opportunity for God to test them on the Day of Judgment?

Your eagerness for the salvation of souls is commendable, but you must employ it in calling to Allah with wisdom and good counsel. Do not grieve yourself to death over those who have gone astray, for Allah knows best who will be guided. Your mission is to convey the message; you are not responsible for guiding people or controlling their destinies. Allah Almighty sent messengers to establish proof against people, not to discover whether they would respond to their call or not. Concealing the truth is a crime against people and a forfeiture of their opportunity for guidance.