I think Canada was a country before the USA became a country so the situation never arose.
Canada was a country on its own by 1867, but the USA was still fighting the civil war at that time, and much of the country we now call the USA had been owned by France and Spain and so the USA as a country was only just being formed.
I think the people in the USA were so busy worrying about to make THEMSELVES into a country they had little time to worry about Canada.
It helps to understand how the USA developed as a country.
If you think of the NAME it is a United States of America.
So it is 50 fairly independant states joining together to become one country, but this did not happen overnight.
When people from Europe first started going to the USA they created their own little colonies or territories, mostly in the East.
These were almost like separate countries, with their own laws, their own money, their own languages (much like Europe is now).
These colonies then became the first "states (hence the name of the country "united states")
The "west" was not really though of as part of the USA at the time and almost all the fighting in the civil war took part in the East of the country, and almost none in the west.
If you look at this map of the USA you will see that the East of the country was lots of individual states, but the middle of the country (where it says Louisina Purchase) was owned by the French, and the west of the country was owned by the Spanish.
http://www.worldbook.com/wb/images/content_spo tlight/lewis_and_clark/lp.gif
And the land ABOVE the USA (what became Canada) was owned by the British (and some of it the French) so we were not likely to give is away to th