Not many Canadian medical schools accept applicants from the USA.
The AMCAS site says that 17 Canadian medical schools are members but that doesn't mean that you can apply to all of them internationally, it just means that they may use the MCAT exam as an entrance requirement
https://members.aamc.org/eweb/DynamicPa ... l%20SchoolI got interviewed at McGill University medical school in Montreal which is the top school in Canada, and submitting the MCAT was optional in their applications
To answer the main question, yes the few programs that would accept you applying from abroad are just as competitive and there isn't a compelling reason for them to accept American students, so being US citizen doesn't have much advantage
My personal experience was that the two interviewers at McGill had an anti-American bias and tried to stereotype American students.