I am sorry that your relative did not like being called Protestant.
However, as an Irish-American Catholic, Anglicans are Protestants to me and my family.
In the USA in past centuries, if you had insinuated that an Episcopalian was a Catholic, he would probably have been outraged. Catholicism was the religion of lower class immigrants. Episcopalianism was the respectable faith practiced by the upper classes whose ancestors had come to USA many generations ago. They were happy to be called Protestants and usually didn’t mind being classed with the Presbyterians at least (they might have objected to being lumped in with Evangelicals).
I recently visited a historic old mining town in USA, the one made famous in the Sean Connery film “The Molly Maguires” which was filmed there. The Episcopalian church was at one end of the town, the wealthy end. They offered to let the Presbyterians use their church for worship, but the Presbyterians refused and built their own church next door to the Episcopalian one. The Catholic church was at the complete other end of the town, in the poorest part.