This could be a complicated subject depending upon the details.
You can buy the phone in the US and use an account set to Taiwan. You do not have to have an ID set to the US to use a phone purchased in the US.
Note that buying a device in another country for use in your home country is not a good idea, but that is another subject. Sometimes trying to save a bit of money isn't worth the trouble. Don't forget that the US prices do not include sales tax which will be added on later.
If all you are worried about is the subscription, you could cancel it and then contact Apple ans ask them to end it now.
This support article explains how to cancel a subscription from Apple on an Apple mobile device, Mac, PC, and online ➔ If you want to cancel a subscription from Apple - Apple Support , or this video will only tell you how to do it on an iPhone ➔ https://www.youtube.com/watch/XXx-J-ueCtE