As an answer to the assertion that the United States of America was created as a Christian Nation, I would offer one of our first National symbols, Columbia - first established in 1730. Columbia is the American Goddess created from Greek tradition (the USA was founded during the Enlightenment period when Greek and Roman ideals were popular, and religion was waning), and was the icon of every mythical good thing about America...Justice, Protection, Wisdom, Adventure, Enlightenment, Bravery, Sacrifice, Invention, Toughness, ... Columbia was popular right up until the Cold War and the induced religious fervor due to fear and opportunity.

I rather like the symbol of Columbia. I see our her diminished prevalence, and the discarding of our true National Motto (E PLURIBUS UNUM) as contributors to why America is on a downward spiral.

Americans have every right to be negative. We have two political parties that aren't worth a shit. Technology is stealing jobs from people, folks are worried that America will become a 3rd world country because of high unemployment.

Consider the source.

"Christian values" is a dog whistle, which explains why Americans are so negative. It translates "If you're not in my tribe, f*@# you."

Okay. Note this Fox survey was conducted in 2018. It does not compare our attitudes over time. It is a 2018 snapshot.
Gee, I wonder what we could possibly have to be negative about in this particular point in history. Americans have been becoming increasingly polarized at least since Newt Gingrich's 1994 Contract With America push. Fox news has been shoveling horse shit and calling it news for decades now, specifically aiming to terrify the conservative half of the nation while convincing them with lies that the other half are some sort of demon-possessed monsters. We are now so politically entrenched as to virtually guarantee governmental gridlock and dysfunction. We have a president who proudly declares he is a (White) nationalist and has blown every dog whistle there is for the KKK and neo-Nazis, giving many millions of Americans ample reason to feel targeted for oppression, whether directly or indirectly. And the icing on the cake is the well-oiled Putin machine of completely fake online "grass-roots" protest promoters specifically aimed at tricking Americans into thinking the absolute worst about each other, and amazingly, countless millions refuse to believe the Russian propaganda machine even exists. Why?? Because Trump and his GOP apologists pooh pooh the notion, damn the actual facts.
Okay, that was a soapbox speech. But the short point is that we are not simply inherently negative. Rather, we have been played and are continuing to be manipulated and purposely divided into alternate subjective world views to serve cynical political aims. At this particular point in history. I have to believe we are at a nadir but that it is possible to claw our way back and turn things around.