When Chicken George is in England in 1849 and bets are taken on the chicken fights, the banknotes have different colors (blue, red). But all British pound notes were monochrome (black on white) until the late 20th century.
A slave woman is North Carolina happily announces to fellow slaves that Lee had just surrendered to Grant in Virginia. How could she possibly know that? General Sherman's Union army in North Carolina did not receive word of Lee's surrender for more than a week after it occurred.
On the eve of the Civil War, Chicken George returns to America from Britain, having been freed by his English master after being held as a slave there for 20 years.. Since the British outlawed slavery throughout its Empire in 1833, a number of years before Chicken George was taken to Britain as a slave, he would have been a free man the second he set foot in Britain, and could not have been held there as a slave for 20 years.
Chicken George is dragged off to slavery in England for decades in around 1830 but slavery was abolished in England from late 1700's with acts of Parliament outlawing it in 1807, 1824 and 1833. You couldn't keep a slave in England at that time.