The most powerful institution in the world in 1517 was far and away the Ottoman Empire.
If the Ottomans had suceeded in their 1529 siege of Vienna - and only a miracle prevented them from doing so - Christianity, whether Catholic or Reformed, would have become an academic question.
Usually in historic context of the 16th Century and before, when speaking of Europe, “World” meant Europe...and Turkey and the Middle East is not Europe.
Far and away the most powerful institution in Europe in 1517 was the Roman Church, powers from outside notwithstanding. And it took a hammer like Luther to break Rome’s corrupt iron fist.