That statement is so astoundingly misguided it defies description. There were innumerable cultural differences between the north and south at that time! Literally innumerable!
I'll agree that there were differences, but with the exception of slavery, they were mostly superficial. How else can we explain the strong support for Lincoln and the Union in the parts of the South with insignificant slavery? In the 1860s the farmers of the Midwest and South were one people. There were slaveowners of the South and industrial interests of the North that were pitted against one another, but the common people of the whole nation were one. In 1860 as in today, the main fault line should not be North/South, but between the heartland and the mindset of the coastal elites.
In my civic identity, I am a Tennessean and an American who happens to live in the South. I am not a Southerner to the point that it separates me from my fellow Americans throughout the nation. As such I hold Abraham Lincoln in high esteem. He was not perfect in his actions, but it was a blessing to our nation that he was the man of the hour.