If you’re talking about Canadian raising, Americans never get it right.
You may want to check out this book. It’s got a lot of information on a wide variety of accents, and it’s pretty easy to use if you want to learn them.
Yes, Americans reduce the “ou” to “oo,” so “about” sounds like “aboot” when imitating a stereotypical Canadian accent, but that’s not the right sound to my ears. I didn’t realize this happens only before voiceless consonants – that would explain why I sometimes hear it, and sometimes don’t. It’s not me missing it, it doesn’t happen all the time. Cool link!