I agree with what you said about Chow Yun Fat's role...I'd say this movie one my favorites of his work. For other movies where he shines, check out All About Ah-Long or Hong Kong 1941. They aren't actioners, so these films really let him develop the characters in those roles.
As for a US remake, I don't see how they can even hope to capture the chemistry of those two characters. I also do believe the immigrant experience has a lot to do with the movie, that's kind of the tough one to overcome. The actors would be even tougher to figure out--Cherie Chung & Chow Yun Fat almost run the show because of such strong performances. It took a really good director to handle this film, and I think the same director would have to be used.
The score too was awesome, not pounded in to your head throughout the film like other HK movies from the era. A lot of elements from the first film such as the simplicity of the score, need to stay in the story and not be over-produced by someone high up, looking to make money off the soundtrack. Don't give it to a major studio or you run that risk.
Only writing this because I just watched it again just now haha!