About two years ago, Industry Canada (Canada's version of the FCC) opted to make thier rules for Marine VHF operation nearly identical to the FCC's.
Since that time, US boaters in Canadian waterways need carry no license unless over 65' or operating a commercial boat.
I never bothered before the change anyways... in 30 years of boating in and around Canadian waters, I can't remember once being bothered by Canadian Customs, Immigration, OPP, or Canada's Coasties... for ANY reason. In fact, I only remember ever even seeing any of the above on RARE occassions... usually major events. The Canadian Game officer is a different story... I've seen him more than a few times!
I-68 forms?.... Check in with US customs? Special INS decals?.... Bah Humbug to US customs! Be like Canada! Make a phone call, get a #!! If Osama wanted to come here, do you think he'll bother to register first?
Heck.. you can just stroll across the river in several places now!