A lot of the differences exist because the US broke away from Britain in 1776. Practices diverged from there. In some cases, the US practice is actually older and less evolved than current British practice.
In Canada, we sort of broke away from Britain about 100 years later. From then on, in Canada, the influences of Britain and the US tended to compete.
As an example, in Canada, we drink our mass-market (i.e. not craft brewed) beer cold, but it actually has flavour.
Matt, Canada's confusion is no doubt the result of not allowing the french to secede. Blansky has america right we love to bastardize anything we can english freng german spanish chinese . If it's spoken we'll "borrow" it mispronounce or misspell it and claim it as our own.
To those who are so enamoured of the metric system I say try building a house using a meter stick. The metric system makes sense for scientific use but the englsh system is based on common practical units used in everyday life.
Perhaps if the english hadn't been so intent on cozying up to europe and prove that the english were europeans too they would also still be using the english system.
A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.