From my reading of the period, I honestly think the only regions that couldn't have fallen to protestantism were in Italy and Iberia. The Spanish already went through what amounted to a reformation of their church structures during the 1400s, with massive anti-corruption campaigns and the much closer linkage of the church and state - coupled with a very militant and missionary version of Catholicism. Portugal had a far more corrupt church system, but was so cut off from the rest of Europe and influenced so heavily by Spain that they would be more likely to follow Spanish example than that set elsewhere. In Italy they were under heavy pressure from the closeness of the church - their form of Catholicism might take on a more liberal bent but it would remain Catholic. I would strongly recommend Diarmaid MacCullough's book The Reformation: Europe's House Divided if you want to learn more about all of this.
France could have fallen to the Huguenots at some point during the Wars of Religion, there are multiple possible PoDs to accomplish that. Germany and Austria nearly fell in their entirety to Protestantism in early 1600 while Poland, Transylvania and Royal Hungary all had very strong protestant powers. I think that about covers the areas that didn't go protestant IOTL.
If the Huguenots had been able to hold onto their supporters in Normandy, particularly in the first couple of wars, then they should be set to eventually dominate France. Though that opens up the question and threat of Habsburg or Papal interference in France earlier on.