Well, if you define “Protestant” as anyone who isn’t Catholic, then yes. But I’m not sure that’s the right way of defining Protestant.
“Protestant - Of or pertaining to the faith and practice of those Christians who reject the authority of the Roman Catholic Church.” - Websters.
I suppose you could say that all churches that are not part of the Catholic Church reject its authority. However, in my opinion, it refers more to those churches that broke off from the Cathoic Church because of differing beliefs… and their offshoots.
Other churches that existed at the same time as the Catholic Church and continue to this day, I would not call Protestant. Also, churches that did not come about because of rejecting Catholicism (i.e. kind of a clean slate startup) I do not think should be termed Protestant.