You wrote:
“Before Constantine and Christianity, Rome had a Pantheon of Gods.”
In case you didn’t know, Rome had a pantheon of gods AFTER Constantine as well. Most Romans were still pagans. Strange that they didn’t know that Constantine had created what you claim here:
“Constantine Hybridized the existing Roman Religion with Christianity to form The Holy Roman Catholic Church.”
That’s just about too stupid an idea for words - and that’s probably why no modern reputable historian believes that.
“At that point Constantine became a “Christian”.”
No, actually Constantine became a Christian in belief BEFORE he was even emperor. Thus, he believed in Christ and His Church BEFORE he even had the power or authority to do anything to any religion.
“So how exactly does Praying to Mary make one a Christian?”
In itself it doesn’t. It also doesn’t make one unchristian.
Pagans and Catholics as well...Constantine forced ALL of his armies to be baptized into the 'religion' whether they believed and accepted it or not...