How hard would it be to get into Canadian residency

if you aren't a canadian perm resident/citizen you won't be able to apply for residency programs in certain provinces. also, they have different streams so if you're considered an IMG (anyone who didn't go to medical school in the states or canada) it is much harder. for example, there are only 2 IMG rad onc positions available in the whole country (1 at university of toronto, 1 at university of ottawa) https://w1c.e-carms.ca/pdws/jsp/pd.do?d=916&p=p3&m=1

for u of t, they received close to 50 applications, interviewed 6, for that 1 spot.

 

as far as returning to the states though, you shouldn't have any problems because all canadian rad onc program graduates are also ABR eligible