What exactly is a Christian? One who believes in Christ, right? Read that passage again. There's nothing inherently Christian about that. Vague terms, like the ones used in the Declaration of Independence and the Constitution, can apply to any religion. Our founding fathers were acutely aware of other belief systems and wanted to allow them to thrive under the American model.

I wouldn't say that America was founded as a Christian nation, as much as I would say that America was founded by Christians as a nation without a state religion. England was very oppressive with the Anglican Church at the time of our founding.

The issue is that a state religion was formed at some point (not sure when) that swung the pendulum back the other way. So instead of being good and righteous, it worshipped the base instincts of humanity (the four Fs, as it were: feeding, fighting, fleeing, and fornicating). It was called "secular humanism". This has been used by the elites to undermine all religions. They do not have missionaries, as most religions do; their tactic is using subversion to gain followers (who will claim it's not a religion, but follow it's teachings devoutly see also: atheism). The Satanists were born from this movement.

There is an important distinction to note here: the Satanists generally differ from the Luciferians in that they are lower class humanists who hate all religion, except their own. Luciferians are higher class humanists (celebrities, politicians, etc), who are basically Christians who believe the bible in a Beowulf/Grendel kind of way (that is to say that Luciferianism is basically Christianity from the perspective of Lucifer).

Satanists and Luciferians more recently paired up with Sabbatean Judaism (basically Satanism for the Jewish faith), who believe that the prophecies within the Torah must be intentionally fulfilled by man. So we have secular humanists, devil-worshippers, and fake jews who want to bring about an end-times scenario, all working together. This should terrify anyone.

Also, to your point about communism and satanism sharing roots, you are absolutely correct. The "holiest" holiday in satanism/luciferianism is Walpurgisnacht. This is May first, May Day, the international workers day, or the Haymarket Affair memorial day.