Bathroom/restroom = washroom. I think I'm the only American who calls it a restroom anyway....
British spellings. The Canadians use the "ou" vs. "o," "re" vs. "er," and to pay someone, they write a cheque. Examples: flavour, harbour, colour, neighbour, fibre, litre.
Coffee creamer = coffee whitener. Huh. Glad I wandered around and found it on my own instead of asking, b/c creamer is not a familiar term here!
Crunchier M&Ms = Smarties. Gone are the chalky, fruity-tasting Smarties of America (sniff.... I liked those little guys), only to be replaced with flatter, crunchier M&Ms, as far as I can tell.
Kraft Mac'n'cheese (blue box) = Kraft Dinner. So in the Barenaked Ladies' "If I had a million dollars, we wouldn't have to eat Kraft dinner... but we would!" they're talking about boxed mac'n'cheese.
Studio apartment = bachelor. Because bachelors can only take care of an apartment if its confined to a single room?
Tim Horton's lingo. There is code for ordering at a Timmy's. 2 creams/2 sugars is called a double-double, 3 is a triple-triple, and so forth. But me, who just wants 1 cream/sugar? This is not a single-single. It is a regular. And a frappuccino is called an ice cap (cute, eh?).
Zee = zed. Still gets me every time because I expect "zed" to be with a British accent.