America a christian nation?

[Anomalocaris]

They were fleeing religious persecution and were very concerned about the need to create a government system

Most of the colonies were founded as commercial enterprises.

Christianity was very much an overt prop for crass mercenary and commercial concerns during much of its existence.

The conviction, calculatingly inculcated by christianity, that "My greed and overweening sense of superiority deserves to be, and therefore will be, gratified at whatever cost to anyone else, particularly nonbelievers, because I am a good pious christian" had been and continues to be the main, (only sometimes) unspoken attraction of christianity.

This was how the Spanish attracted recruits to exterminate natives of central and south america for their gold and silver, but in the name of their salvation. This was how the British colonies justified their existence in North America, this was how American settlers justified spreading over much of North America and dispossessing the natives, and this continue to be how megachurches fill their pews with the gullibly grasping.

As to why America may continue to be seen convincingly as a christian nation by the foolish, uneducated and the gullible, that's because the gullible have been indoctrinated with the notion that America is the exceptional land of economic success, as well as the false association between economic success and christainity.