Common Apple ID across 2 different country phones

Yes, you could use the same Apple ID since phone service has little to do with an Apple ID. However, an Apple ID can only be set to one country at a time so if you are using apps or other services that are country-specific you may encounter issues. You could try changing country but this could be a nuisance if you have to do it frequently. The alternative would be to have two Apple accounts, each set to the country for which the phone is being used. You'll need separate email addresses etc. since you are basically setting up two personas.

This document explains how to create a new Apple ID (create an Apple Account) --> How to create a new Apple ID - Apple Support

This could start to be a complicated subject depending upon how exactly you wish to configure things. You could, for example, still get all your email on both devices since you can have the Mail app check multiple accounts.

MrHoffman wrote:

Set up Family Sharing for your two country-specific Apple IDs,

That is not possible.

Legal - Apple Media Services - Apple

"All Family members must share the same Home Country."

Share purchases with others in your Family Sharing group on Mac - Apple Support

"To share purchases, family members must be in the same iTunes Store country or region."

I don't know if this is workable but many newer iPhones have dual SIM capability. Since you don't really seem to need two IDs you could use dual SIM to have two different phone services but then use a single ID.

Using Dual SIM with an eSIM - Using Dual SIM with an eSIM - Apple Support

iPhone XS, iPhone XS Max, iPhone XR, and later feature Dual SIM with a nano-SIM and an eSIM. An eSIM is a digital SIM that allows you to activate a cellular plan from your carrier without having to use a physical nano-SIM.

Here are a few of the many ways you can use Dual SIM:

Use one number for business and another number for personal calls.

Add a local data plan when you travel outside of the country or region.

Have separate voice and data plans.

What you need

An iPhone XS, iPhone XS Max, iPhone XR, or later with iOS 12.1 or later

A wireless carrier that supports eSIM

A related article:

Use Dual SIM on iPhone - Apple Support

Set up Family Sharing for your two country-specific Apple IDs, keeping your mobile numbers separate and keeping your country-specific payment info separate, and sharing your own local content.

Some subscribed or rented or app-related stuff will only be available from one country or the other (and thus from one device or the other), and you’ll probably have carrier issues with being away from one or both plans. Much akin to Apple and the country-specific Apple ID requirements, mobile carriers might (will?) detect (mis-detect?) longer-term international forwarding within their systems.

Might need to host your own mail and sharing services too, so a tangled ID somewhere doesn’t block something critical for access recovery.

The world is very intentionally not set up for this. Operating this way at the two-international-subsidiaries budget can be quite workable, sure. But not for operating at the two-iPhones budget.

Check some “ex-pat” emigrant forums for some ideas and options here, too.

You can use one Apple ID on 2 iPhones, but because of the difference in region you might want to have. 2 region bound Apple ID's to make sure that you can use the App Store of the right region