Some back of the envelope calculations:
Length of US/Canada border: 8,890km [1] Population of Canada: 36,708,083 [2]
Assuming ALL of Canada's population lives within 100km of this border a rough estimate of this area might be 889,000km^2 giving a population density of 41 people per square kilometre. This conservative estimate is in the same ballpark as the US population density of 33 people per square kilometre [3] with the caveat that this population is spread across a long, thin 9000 km ribbon increasing the cost of roads and any other infrastructure versus the US's more favourable shape. And let's not forget that Canada's GDP per capita is $46,437 while America's is $57,467 [4]. This is a factor of 1.24 in favour of the United States.
Given all this, why is the US incapable of providing the kind of single-payer healthcare that Canada does to its population?
[1] https://www.statcan.gc.ca/pub/11-402-x/2012000/chap/geo/geo-...
[2] http://www.statcan.gc.ca/tables-tableaux/sum-som/l01/cst01/f...
[3] https://en.wikipedia.org/wiki/List_of_countries_and_dependen...
[4] https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(PPP)...