I can echo the dissent to this view. Not one european nation came out as a turf for religious freedom. Quite the opposite, most nations came out as religiously cleansed.
Ethnicity, Religion and Nationhood are different things. Todays meaning of "nationhood" was probably formed in this time of wars. But most of Europe's nations of present day are culturally dominated by one the belligrent religions:
Catholic: Italy, Belgium, France, Austria, Ireland, Poland
Protestant: Great Britain, Netherlands, Scandinavia, the Baltics
Today, there are only two exceptions. Switzerland and Germany. Germany didn't exist as a "nation", but in each of the many German states, it was either one or the other religion. As was the case in Switzerland's Cantons.
Swiss history can be thought of periods of peace and war. By peace, I mean sending mercenaries to go fight, and burning jews and witches instead of invading the neighboring cantons with a slightly different version of Christianity and pillaging them.
Fortunately, the invention of the portable Raclette oven calmed down religious tensions, though it did not lessen the zeal for witch and jew burnings.
There should be no conflict here. The idea arose out of a period of intense conflict. This idea arose as a response to religious conflict, and took a long time to get accepted. It is therefore no surprise that there was a lot of religious cleansing prior to and during the period where the idea formed.
More specifically, modern notions of religious freedom generally get traced back to John Locke's Letters Concerning Toleration (1689–92). He was influenced in turn by ideas developed by Baptist theologists. And his sphere of influence includes people like Thomas Jefferson who put freedom of religion into the First Amendment of the US Constitution.
Ethnicity, Religion and Nationhood are different things. Todays meaning of "nationhood" was probably formed in this time of wars. But most of Europe's nations of present day are culturally dominated by one the belligrent religions:
Catholic: Italy, Belgium, France, Austria, Ireland, Poland Protestant: Great Britain, Netherlands, Scandinavia, the Baltics
Today, there are only two exceptions. Switzerland and Germany. Germany didn't exist as a "nation", but in each of the many German states, it was either one or the other religion. As was the case in Switzerland's Cantons.