A world where the German "Peasants War" of 1524-1526 went rather differently...in 1600, the Federation has held its own in three major wars, and with the aid of the Ottomans and the distraction of the Dutch has driven the Habsburgs from Austria and Bohemia, and opened a land corridor to the Netherlands allowing for effective pooling of forces. A side effect of the survival of the Federation is the breakup of the Swiss Confederation, with the "old core" Catholic states remaining seperate, although neutral in the wars between Spain and its allies and puppets vs the German Christian Federation.
"Christian"? The Federation is mostly protestant. What _kind_ of Protestant, is another matter. As well as Calvinists, Zwinglians, etc. and even some Lutherans (he still has his apologists for all the Bad Things he said about the peasant rebels), there are offshoots of Protestantism that do not exist in our world. Most of the peasant-dominated districts follow a sort of moderate Lutheranism-offshoot which downplays the pre-destination bit and looks a bit like Catholicism with no pope and elective priests, while more "hardline" versions of Protestantism are growing more popular in the cities.
Although so far the Federation has held together out of hostility to Church and emperor, some worry that the internal contradictions of the Federation, with its divisions between city and country, moderate and extremist Protestantism, German and Czech, not to mention the conflict between the centralizing government, the rich and powerful men of the Grand Council, and autonomy-minded local governments, will eventually break it apart. Much depends on how the current religious turbulence in England will play out, and whether the results will be a new enemy or a new ally...
(Given three quarters of a century of butterflies, the religious and political situation in England is rather different from OTL 1600).