Canadian citizens who earn their MD from US medical schools are eligible to sit their Canadian medical exams & apply for residency (post-MD clinical training) positions in Canada.
However, Canada limits the number of residency positions to the numbers of Canadians expected to earn their MD degree from Canadian med schools. So it might be difficult to compete for a residency position. Depends a lot on which med school you graduate from & how well you do.
US & Canadian med schools both offer MD degrees, and are very comparable in their education, training. Other than competition for residency positions - difficult, very competitive, in both countries - a US MD degree is completely acceptable on same terms as Canadian MD degree, and vice versa.