Yes, southern rock was influenced by negro spirituals, blues and jazz, but its roots go all the way back to ancient Scots-Irish musical traditions.
OTL At risk of over-simplification: the antebellum South had only 3 social classes: plantation owners, black slaves and white trash.
Plantation owners were among the first (non-native) settlers. Many came from wealthy European families that could afford to pay top dollar for the best farmland along rivers.
Planters soon imported millions of black slaves from Africa to work their fields, raising cash crops like: tobacco, cotton and sugar cane for European markets.
Meanwhile, late-arriving immigrants tended to be poor Scots-Irish farmers. By, Scots-Irish, I mean descended from the multiple waves of Scots who invaded Ireland to establish "plantations" and displace traditional Irish-Catholic nobility. In North America, those poor SI farmers were forced into subsitance farming up in narrow mountain valleys (hollows). Because the soil was so poor, Scots-Irish became hillbillies (an Irish term) while retaining their stringed instruments and penny-whistles. Because the industrial revolution largely by-passed hillbillies living in the Appalachian Mountains (Alambama, Georgia, Kentucky, Pennsylvania, West Virginia and the Ozark Mountains of Arkansas) that long-term poverty helped preserve old-time Scots-Irish music.
It is amazing how the ruling Southern planter elite were able to recruit so many hundreds of thousands of white-trash SI to defend planter values during the American Civil War. Recruitment included large numbers of Irish refugees - just off the boat - fleeing the Irish Potatoe Famines of the 1840s.
This new wave of Scots-Irish immigrants displaced blacks at the lowest level of the Southern economy by becoming day-labourers who did the most dangerous work like draining snake-infested swamps or breaking horses to the saddle.
Come the industrial revolution, wealthy elites invented new ways to exploit poor whites by forcing them to work for low wages in cramped, dangerous factories or deep in coal mines.
During Prohibition (1920s) hillbillies found lucrative outlets for their traditional, home-brewed, moonshine whiskey in thirsty towns across America. Hillbilly music was as popular in (illicit) saloons as black blues and jazz. In many respects, Prohibition was a racist/xenophobic attempt at suppressing hillbilly moonshine, German-American beer gardens, etc.
How moonshining differs from modern, dirt-poor Afghan farmers growing marijuana or hashish or opium poppies is a mystery to me?????
Fast forward to the Vietnam War, traditional army recruitment policies returned to the Deep South. Steve Earl sang about "volunteered for the army on my birthday, they take the white trash first round here anyways ...."
Meanwhile Bruce Springsteen lamented about the miserable treatment of returning veterans in his song "Born in the USA."
Disgruntlement about the huge numbers of white trash dying in Vietnam motivated folk musicians, Southern Rockers, etc. to write protest songs about the VN War. Many of those songs were written about poor whites being used and abused to fulfill "planter" ambitions.