William Adams, known to the Japanese as Muira Anjin had been born in England but became a Sailor.
So to sum it up he landed in Japan and was taken in by the Shogunate and given a position to design the new Japanese navy and introduced the Red Seal Ships. He was then one day asked by Tokugawa Ieyasu about what he believed in he said "in God, that made heaven and earth."
https://en.wikipedia.org/wiki/William_Adams_(sailor)
But later Ieyasu had demanded Christians abandon their faith.
But what if he had converted to English Protestantism? His friendship with William Adams was apparent and it would not have been too much of a stretch.
This may reverse the entire isolationist policy the Tokugawa Shogunate enforced, or it could still be in place but with a slight bit of lenience for religious and political matters.
They could try to imitate the Europeans style of Imperialism and attempt to try and take a whack of the large Islands north of Hokkaido much earlier? Would they Even try and get some Siberian Territory and Establish a city in what would be Vladivostock?
Could Russia consider selling Alaska to the Japanese instead of the Americans?
If the Japanese improved their Naval Technology a bit could they get into wars with some smaller European powers like the Portuguese or the Dutch?
Not to mention about Christianity inevitably bringing about
loads of Western Influence, they might even throw the Hiragana alphabet out the window and just use the Latin Alphabet to make things easier. They might even begin to use Forks and Spoons!
The possibilities are Endless, I could possibly make a TL out of this but I already have two going on and (relatively) Modern TL's like this are hard to work with so you people are free to make a TL about it if you want.