Thinking about St. Joan of Arc and the English Reformation--I remember hearing the celebrant of Mass on EWTN on her feast day a few years ago mention that if she had not led France in defeating the English during the Hundred Years War, at least of part of France (more than Calais!) might have been under English control. And that would have had consequences.
St. Joan was burned alive at the stake on May 30 in 1431. In 1531, one hundred years later, Henry VIII started his break away from the one, holy, catholic, and apostolic Church. In May of 1532 he forced the Convocation of Bishops to acknowledge his authority over the Church in England "as far as God allows", and proclaimed himself through Parliament to be the Supreme Head and Governor of the Ecclesiae Anglicanae in the Act of Supremacy three years later.
Thus if St. Joan of Arc had not helped rally France to defeat the English, "France" would have participated in the English Reformation, her great monasteries suppressed (250 years before the French Revolution's suppression), statues and paintings of Notre Dame crushed and burned along with other great Christian art, and many glorious Gothic cathedrals despoiled and destroyed, their shrines and relics, treasures and art plundered--Chartres without the Sancta Camisa, Sainte Chapelle without the relic of the Crown of Thorns--again anticipating much of the iconoclasm that did occur after the French Revolution. But without St. Joan of Arc, hearing the voices of the saints, going to her country's weak king, and leading France to victory, France would have been Anglican (Protestant) in the 16th century, and western culture, Catholic culture, would have lost the same things in France as were lost in England: art, music, visual beauty, books, monasticism, and worship.
O God, Who didst raise up the Blessed
Maiden Jeanne to defend Faith and fatherland, grant to us,
we beseech Thee, by her intercession,
that Thy Church, overcoming the snares
of the enemy, may rejoice in a perpetual peace.
Through Our Lord Jesus Christ.
She was canonized in 1920 after having been beatified in 1909: three miracles were accepted as demonstration of her sanctity. More about her canonization here.
This website suggests other aspects of an alternative history without St. Joan of Arc:
What events might not have happened without Joan of Arc saving France? Without Joan of Arc it is very doubtful that France would have become the strong unified nation that it became. Without a strong France many of the later events that occurred in Europe and around the world would have been much different. It is even conceivable that American independence from Britain would never have happened because it was the French military assistance that made the difference and directly caused the surrender of Cornwallis at Yorktown.
Do you think France would've existed to this day without Joan of Arc's actions? Joan helped to give the people of France a national identity. Before Joan people would identify themselves as being from parts of France such as people from the region of Burgundy calling themselves Burgundians. After Joan of Arc the people were much more likely to identify themselves as being French. It was having a national identity that helped forge the great nation that France became and still is today.
In one of those strange ironies, the Church of England honors Joan of Arc on their liturgical calendar--as a visionary (not necessarily because her visions were true, but because she listened to them)! The Catholic Church honors St. Joan of Arc as a martyr and virgin, unjustly condemned to death; a holy Maiden who loved Jesus, Notre Dame and the saints.