Sicilians were sometimes "black" in the jim crow south. I couldn't find the citation, but at least one black dude avoided getting murdered after it was discovered the woman he was sleeping with was sicilian. I think the anecdote is from Isabelle Wilkerson's Caste.

Did you not read the end of the article you linked? His wife definitely had black roots, but it was a family secret.

Earlier this year, the mystery of whether Vivian was descended in part from Africans was finally resolved. In a February episode of the PBS show, “Finding Your Roots,” host and historian Henry Louis Gates Jr. presented Rosanne Cash with her DNA results and family genealogy. Vivian Cash’s maternal great-great grandmother was indeed an enslaved Black woman, Sarah Shields, whose White father in 1848 had granted her and her eight siblings their freedom and their passage into Whiteness, too.

Basically Vivian's great-great-grandmother was a black enslaved woman, and her descendents hid this fact to save themselves from Jim Crow laws.

It's possible she and Johnny knew but kept it quiet because they lived in the deep south in a time when it was scary to be in any way black. The 'one-drop rule' is still a thing for a lot of americans, after all. We know that Vivian wife was living in fear of the KKK whenever he went on tour. I would imagine he said whatever he had to say to keep her safe while he was away

A few years ago, I visited Jamaica and was surprised to find out how much everyone there loves Johnny Cash. I was anticipating Bob Marley to be the big name, but it was actually Cash. Didn’t even know there was a connection between him and the country

He had a house there, which I had the chance to visit. I'm quite certain he spent most of his time there. Given his immense popularity in Jamaica, it would be shocking if Johnny Cash had held any racist views.

I'm of Sicilian heritage and Cash's first wife, Vivian Liberto, would look perfectly at home at a family reunion.

I won't neuter my dog,

But my truck is now a man,

After putting truck nuts on my large Dodge Ram.

I ain't even going to lie. That was my jam in the 80s.

Yeah, just as an example -

Marty "Big Iron" Robbins released a song in 1966 called "Ain't I Right" that said people who came down to southern towns last summer to show people a new way of life were actually a bunch of secret Communists who didn't care about America and just wanted to sow discord.

Some context: in the summer of 1964, a bunch of civil rights activists went down to southern states to register people to vote for an event called "Freedom Summer," which led to them being harassed by local police and eventually at least 3 of them being murdered by the KKK. This was a huge headline dominating story that made the American mainstream actually start paying attention to the civil rights movement and start looking at how bad racism in the south had gotten, so Robbins was totally reacting to and trying to push against that change in popular opinion when he released that song.

He toured with Rockabilly artists more than other country singers.

But why?!

Oh, you poor soul.

Here's the wikipedia, if you wanna read.

And here's a video about the history of slavery and its after-effects that is kind of relevant.

The tl;dr is that there were laws, like vagrancy (i.e. not having a job), that were vague and applied to "everybody" but realistically only applied to black people through legal jiu jitsu and selective blindness on the part of police. Sundown towns are known as such for that behavior. They were (are) very unwelcoming if you're not white.

Black people who are passing through have to leave by sundown. There's still some small towns in the US with this expectation, although it's no longer written on signs.

A town in the USA that the excluded non-white people from the community...coming from signs that warned non-whites saying "don't let the sun set on you in whatever city".