Did the Catholic Church ever officially teach that all Protestants go to hell?
No. Some individual Catholics may have taught that, but that has never been the official position of the Catholic Church. In fact, in the 1950s, Father Leonard Feeney, SJ, was formally excommunicated for teaching that only baptized Catholics could go to heaven. He was reconciled to the Catholic Church, but it never accepted his teaching on this subject. God is not waiting for our instructions about who should be admitted to heaven.