You wrote:
"What year did the Roman Catholic Church marry the state under Constantine?"
There was no marriage of any such kind. The Roman state stayed the Roman state. The Catholic Church stayed the Catholic Church. The two cooperated, but NEVER became one. If the two became one then why did Constantine and his sons flirt with Arianism when the Church opposed it? Why was Constantine baptized by an Arian heretic? Why were one or more of his sons Arian, openly Arian at that? If the Roman state and Catholic Church were one then why didn't the Church ever accept Arianism when Constantine and his family championed it several years AFTER the Council of Nicea?
"I've always believed that is the point where Roman Catholicism really went off track becoming more political than religious."
And that never happened. The Church was never more political than religious. The Church offers Mass every day. How often does it hold political conventions? The Church has seven sacraments, but no public political parties. The Church has the Bible, but didn't change a word of it to please an emperor, or king, or noble of any rank. Please don't go trolling over the internet looking for Davinci Code like conspiracies that say otherwise. Why waste your time?
"The Church was never more political than religious. The Church offers Mass every day. How often does it hold political conventions?"
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What do you call it when your Cardinals meet and ELECT a Pope?