回复：请教: 境外申请EB1A （Ｉ－140）

It seems it is possible to apply for EB1A (I-140) in Canada.
-Correct.
Does an offer letter help such application?
-No for EB1A I-140.

If I-140 approved, how to apply for GC?
-Apply for the immigration visa in the US Consulate in canada.

Do I need to find a job then apply for I-485 or apply for immigration visa in Canada (but I cannot find the information)?
-Yes. You can not file I-485 outside US, but apply for immigration visa in Canada. You need to get a job offer from a US employer before you apply for the visa outside US or file I-485 within US. That is why it is called employment-based.


Which one is better (pros and cons) between using TN to apply EB1A in US and apply Eb1A in Canada (with an offer letter)?

Thanks for comments and suggestions!