Is it harder for non-Canadian or non-American people to become a doctor ?

[nato]

Hi.. as the title says, I am from Taiwan (not sure if anyone knows ..it's a small country in Asia) My mom kept telling me that holding either American or Canadian citizenship would help my career in North America, but I am not either of them. It must be a remour ..right? I just need good grades and get prepared, so I can get a work visa and evntually apply for citizenship?
I dont understand everything ..so please tell me more infomation about it.. :hail::confused: