The Pope has authority to change, not the Lord’s Prayer itself, but the translations and theological interpretations of the Lord’s Prayer. However, the Holy See should do this carefully, clearly, and systematically, and unfortunately this was not done. For example, if you google “changes to Lord’s Prayer” you will find stories from CBS, NPR, The Economist, The Irish Times, the Huffington Post, Fox, and CNN, and every other unofficial and theologically-uninformed source, but nothing from the Holy See! The Vatican website has nothing about the Pope's change in how we pray the Lord’s Prayer, the “perfect prayer,” the most fundamental expression of the Christian faith.
Having heard all about "changing the Lord's Prayer" on NPR or CNN but not from the Holy See, parish priests and bishops are scrambling to cobble some explanation for their people. In their Sunday homilies, thousands of priests will attempt to explain “what the Pope means," and most of us will not do a good job. But if the Holy See will not offer clarity, the lesser shepherds will have to do their best. Here is my attempt.
The closest text we have to Christ’s words (the Greek) clearly say “lead us not into temptation” or trial or test. Anyone who has suffered a test of faith through serious illness or death or betrayal or any of life’s sufferings will pray this prayer fervently. “Lord, you know best, but please: if there is any way I could avoid this cup let it pass from me.” Lead me not through this trial is of course Christ's own prayer the night before His crucifixion. Yes, the Pope’s native Spanish translation is a little inaccurate (No nos dejes en tentacion—"do not let us fall into temptation"), but the Greek is clear, and the theology is clear: we should pray, like Our Lord, to be spared great trials, but if it pleases God in His ineffable providence to lead us through “the shadow of the valley of death,” we should do our best to submit to his perfect will with joy.
The Church is suffering great confusion at this time, but even this confusion is a "temptation" that God permits for a greater good. In one of Isaiah's great Messianic prophecies, God was "pleased to crush his servant" (Isaiah 53:10, but please read the whole passage). Let us believe that He "leads" us through dark valleys only for our greater good. It is the stuff of which great saints are made. God “led” Mother Teresa through a dark night for fifty years, in which she felt that God had abandoned her, hated her, and condemned her to hell. “I am the most hated one,” she wrote in her diary. She had lost all sense of faith, and yet only this great “temptation” could open her heart to receive the infinite God. People wonder how Mother Teresa could love the poorest of the poor so deeply as to become one of them. The fifty-year long trial of faith through which God led her is the answer. By “leading us” through temptations, and that means going ahead of the one being led, "leading us by the hand," God leads us to heaven.
Let us hope, in a time of anguish and confusion for the Church, a great trial in which many Catholics feel abandoned by their spiritual fathers, God will purify our faith in Him alone.