Thomas Pain did have an advantage for not being native born, in the prospect of realizing America's much needed freedom. Pain was a government official, so Pain knew of the flaws of the British government. Who else would have been a better champion of the American Independence than someone who lived through the corruption of the British parliament?
Thomas Pain's audience was the average commoner. Thomas Jeferson's intended audience was educated people; merchants, property owners, and government officials.
I believe the reason why slavery was not included in the declaration of independence, was because Great Britain was offering slaves the chance to be free if slaves join in arms with the British Army.
Thomas Jefferson described