Not sure what this has to do with Amendment I, but Christianity is very well established throughout North America.
The First Amendment guarantees freedoms concerning religion, expression, assembly, and the right to petition. It forbids Congress from both promoting one religion over others and also restricting an individual’s religious practices. It guarantees freedom of expression by prohibiting Congress from restricting the press or the rights of individuals to speak freely. It also guarantees the right of citizens to assemble peaceably and to petition their government.
https://www.law.cornell.edu/constitution/first_amendment