There were plans drawn up by the UK for conducting warfare in N. America, with the specific aim of countering a US invasion of Canada, the purpose of which would be to deny the port of Halifax to the Royal Navy. During this time, Canada drew up contingency plans for invading the US and fighting off an invasion. Britain hoped that the Canadians would be able to defend Halifax, but had no plans to bail out Canada in this circumstance. The US drafted a plan for the invasion of Canada, while the UK drafted a plan to defeat the US Navy at sea.

I think there's a Nova episode about all this.