Generally and logically, international mail will take longer--international mail, from Canada to USA varies, just like it is from USA to Canada. It depends on the country's Postal Services. Regular mail such as letters, flyers, etc. will usually take anywhere from 2-4 days, locally and states nearby will usually take 1 day, however, packages or items in bulk can take longer, especially if it is delivered 3rd class which can take up to a week and much longer. Consumers who desire to have such a package (goodies like cookies, gifts, etc.,) arrive early will go with the priority mail which is 2 day mail, at most 3-4 days depending on locations.
It would be safe to say that a letter from Canada to the USA will take 4 to 7 days.
Hmm...expecting something ummm...
(ofc, I'm j/k with you)
(how do I know about the P.O.? I've worked there years ago--