Well, for a lot of thing, Canadians really are pissed at the US.

Just think of what would happen if any other country than the US did the following:
- sneak nuclear subs into sovereign waters of a peaceful nation
- impose duties and tariffs with a country that has signed a free trade agreement specifically to get rid of those duties and tariffs (and cause 30% of an primary industry to be laid off)
- arrest citizens for legally trading with a third party country, even though to NOT trade with that country is illegal (as trading with Cuba is in Canada)
- develop power plants and other industrial plants next to sensitive border points without regard to the pollution that is created in residential areas (Sumas BC is one small example)

There are plenty more...and think of turning the tables: what would happen if another country did these things to the US?