Imposing sanctions on India or blatantly seen to be siding with Pakistan in this tussle are the least likely options that US or western European nations or even China & Muslim countries will want to exercise.
Article 370 and 35A do not target any caste, creed or religion. There is no seizure of land from people living there. All it seeks to do is to provide them with same rights as the rest of India enjoys.
A lot of factors would need to be weighed before the move is made