Both shared the main grievances with England that energized the dispute. Both resented the taxes that were instituted to pay for administering the new territory of Canada and for resident English troops ( the colonies had previously depended on militias, which hadn't worked that well when there was an actual war). Both resented the limits placed on westward encroachment into previously French, now Native territory, expecting the defeat of the French would result in more lands for settlement. So, in the deliberations in the Continental Congress there were southern voices as well as northern ones pushing for revolt, like Richard Henry Lee and Thomas Jefferson. And after the clumsy English reaction to the grievances, there were also some who became convinced that independence was inevitable and joined, like William Hooper.

When the revolt in Boston spread to New York and seemed impossible to contain, General Henry Clinton did try to move his forces south, expecting that the higher number of Loyalists there would make it easier to subdue the revolt in those states. Once that was done, it should have been easier to deal with the northern colonies. But Virginia governor Dunmore and Clinton both offered freedom to any slaves who escaped and joined the British army. This alienated a lot of the Loyalist slaveholders. And, while most all the colonies were quite rural and pretty sparsely settled, the south was even more rural than the north, and the relatively small British forces were never able to actually occupy and control territory. The Loyalists who agreed to cooperate with and help the British forces also discovered that the British army was unable to be present to keep them safe from Patriot reprisals, and as a result were not able to significantly assist.

The Virginia gentry's efforts to shape London's imperial policy were thwarted by British merchants and by a coalition of Indian nations. In 1774, elite Virginians suspended trade with Britain in order to pressure Parliament and, at the same time, to save restive Virginia debtors from a terrible recession. The boycott and the growing imperial conflict led to rebellions by enslaved Virginians, Indians, and tobacco farmers. By the spring of 1776 the gentry believed the only way to regain control of the common people was to take Virginia out of the British Empire.

​

Source: Forced Founders: Indians, Debtors, Slaves, & the Making of the American Revolution in Virginia by Woody Holton.

In addition to the arguments above, the legal decision in "Somersett v. Steuart, often seen written as Somerset v. Stewart" put forth on June 22, 1772 played a role, too.

This was the first ruling in which British courts emancipated an American-Colonial slave and put doubts into the ruling plantation class as to whether the slave system could/would continue under British rule long term. This ruling was a direct threat to class power of the Southern elite and anyone making money from the slave trade.

Sources:

https://time.com/5857402/confederate-monuments-american-revolution/

Which pulls from

A. Leon Higginbotham Jr.’s 1978 In the Matter of Color and 2005’s Slave Nation by Alfred W. and Ruth G. Blumrosen.