The first amendment

Part of the first amendment says “congress shall make no law respecting a religion”. I get the impression that lawyers and others believe a wider context but let me give an example. If a court has a plaque of the Ten Commandments or a government building has a Christmas tree then someone decided to put those up but congress never made a law saying that all courthouses shall display the 10 commandments or that every government building shall have a Christmas tree etc. Based on a literal reading of the first amendment, separation of church and state is not spelled out the way that it seems to be interpreted as

If I look up separation of church and state on Wikipedia, it does not reference the first amendment so much but it gives me this:

The concept originated among early Baptists in America. In 1644, Roger Williams, a puritan minister and founder of the state of Rhode Island and The First Baptist Church in America, was the first public official to call for "a wall or hedge of separation" between "the wilderness of the world" and "the garden of the church."Although the concept is older, the exact phrase "separation of church and state" is derived from "wall of separation between Church & State," a term coined by Thomas Jefferson in his 1802 letter to members of the Danbury Baptist association in the state of Connecticut. The concept was promoted by Enlightenmentphilosophers such as John Locke.