Calling non muslims kafir

[Qweer]

Aoa my question is regarding the nonmuslims of today kafir or disbelievers as islam may not have reached some of them in a way it should like terrorism and its being directed to muslims by western worlds etc and islamophobia i read somewhere that if one believes that a Christian or jew can go to heaven then the person becomes a disbeliever himself so i want to know the ruling regarding this and if its safe to do so and by calling somone (a non muslim) disbeliever one himself would not become a kafir i