The game/movie is not set in Kanto where Red and Brock are from. Unova and Alola are both specifically based on the US and Kalos is a very thinly veiled France. Don't be surprised if the next game is in London (or "Poke-London").
We don't know which region Rhyme City is supposed to be set in, they most likely kept it purposefully vague, but considering all of the NPCs in the game and the fact the main character is called fucking Tim Goodman, it's most likely not supposed to be Japan.
Pokemon has evolved far beyond its roots as a Japanese videogame and is now a multicultural international franchise, arguably the biggest in the world. If the movie were about Red setting out on his adventure from Pallete town, then yes, I'd argue they should use a Japanese actor for him.. But it's not and your argument is completely asinine, even if you are trolling.