You are fudging by mixing up the Seven years War, the ARW and the Napoleonic wars . . . In the case of Japan, England (not Britain in this case) had had a good connection since Will Adams had been Iyasue's naval adviser.
Aren't you now discussing how 18th century japan had a good connection because a man in the 17th century?
One just repeats the Indian, Malay and Burma experience. Local troops, stiffened by naval assets, a whiff of artillery and a couple of companies of grenadiers.
Japan was not India, Malay, or Burma. It was a centralized state with a strong (despotic) government.
This isn't that much different than saying you could invade 18th century Britain with help from the Earl of Cornwall.