In the colonies, Cotton Mather learned about the practice from on of his slaves and recommended it.
Smallpox killed about 30 percent of people, and left many survivors blind or scarred. Variolation cut the death rate to 10 percent.
Vaccination with cowpox derived vaccinia has less than one percent mortality.
Washington used variolation on new recruits because there was smallpox in nearby Boston and probably saved the revolution
Ironically the invasion of Canada failed due to smallpox, and many black slaves who joined the British to fight in exchange for freedom died of smallpox.
Link correction of smallpox
900-1000 AD. The first precursor to a modern vaccination, however, occurred in China. The Chinese were the first to develop a primitive form of a vaccine around the 10th century, according to the NHS. Known as variolation or inoculation, the method was developed to prevent smallpox — a destructive disease that frequently plagued Europe and Asia in the Middle Ages. Chinese physicians discovered that when healthy people were exposed to smallpox scab tissue, they were less likely to get infected with the disease later on (or if they did, it was a much milder, less dangerous version). The most common form of inoculation in China was to crush smallpox scabs into powder, then breathe it in through the nose.
I agree. In one of his letters to his wife Abigail, John Adams said that (paraphrasing) the pox has killed more of our men than the British. It was a real problem.