USA - xCanada - USA can be cabotage, or it might not. IIRC if both legs were on AA it definitely would be cabotage - two US destinations with a foreign connection without stopover; however I believe the fact that YVR-JFK is on another airline means it dodges the cabotage rule. As suggested, the RTW desk (more specifically the tariff/rates people) would flag this if it were an issue. But as I say, I don't think it is because the carriers are based in different countries.

You can certainly protect yourself on this by making YVR a stopover point.