+1 for everything said already. Actually I did usa training and canada training and both were good but different. As for getting the rating on a tc licence the easiest option by far is just to do the rating in canada. If you have a tc cpl already its a no brainer. Strictly speaking, as the op said, its an endorsement not a rating ie a signoff to add priviledges to an existing licence. In the faa world its a different class rating, ie sngle engine sea vs single engine land.There are conversion routes but they are way more complicated than just doing it in canada if you already hold a tc licence unless of course you can find a tc instructor/examiner who can sign you off in the usa if you really couldnt travel to canada. The solo to + landings have been subject to firm scrutiny by tc in the past and I doubt you will find anyone to permit you to do those in the usa easily so even if you got through the faa route youll be going to a canadian float school for those anyway.