In North Carolina, mandantory for operators under 26 only and more than 10 hp.
I think our cut-off is 9.9hp or more and 3m or more in length.
I can't remember, I got my card back in 1999, when they first brought it out.
In Canada there was a 10 year phase in period, depending on age of operator and size of craft. I think the 10 years is up now.
I haven't had a boat for 4 or 5 years now so I am a little out of touch with the regulations