American here, I can't speak for Canada, but I don't think I've ever heard any Americans in the US in real conversations say it differently than it is in Star Trek.
I've lived in nearly every major region of the US, so if there's a place where they still pronounce it like "dah-ta" it must be a very small regional thing. Normal working class people having actual conversions everywhere I've ever been say "day-ta".
I've read before that Patrick Stewart is the reason for that changing, but I don't know if that's true. Seems like an outsized influence for one guy to have on culture, but maybe!
I can't tell if maybe you're joking, but is there another way to pronounce decal? I could in theory imagine someone saying it like "dick-al" but that seems unlikely.