[TheCoelacanth]

> The US was founded by entire colonies of people coming overseas to worship the Christian God freely

That's the source of some of the colonies. There were many other reasons that people came.

Some were looking for economic benefit. Some were prisoners that their home countries were looking to get rid of.

> Christian prayer and Bible reading was a public school item until the mid 1960s

Until the 1960s, but starting in the 1940s or 1950s. Much of that public religiosity was a response to the Cold War, opposing the anti-theistic position of the USSR.