Has the united states ever attacked canada?

In 2003 the American government became quite irate when members of the Canadian government announced plans to decriminalize marijuana. David Murray, an assistant to U.S. Drug Czar John P. Walters, said in a CBC interview that, "We would have to respond. We would be forced to respond." . However the election of the Conservative Party in early 2006 has halted the liberalization of marijuana laws for the foreseeable future.