Idk much about international schools tbh, but i know people who were international that got into Colorado and UVA. I think in general the consensus for international schools for applying is volume like 30+ schools. Pretty much just apply anywhere that will take international students. Good luck.
(P.s Some people in this thread may not recommend you apply to HKU and Duke-NUS, because there not american MD's but if your happy with practicing and living in Singapore and HK as a doctor, especially as a native speaker I think thats perfectly fine and you would be a good fit. )