Since A2P 10DLC requirements for business texting is a movement started in the U.S.A., affects only U.S. phone numbers for now.
While the providers who are leading the initiative are AT&T, T-Mobile, and Verizon most cell phone traffic travels on their networks - meaning that the A2P rules apply to everyone.
Also, Canadian mobile carriers may introduce registered A2P 10DLC solutions in the future, but at this time carriers have not announced any plans to do so.
If you do any business with US-based contacts, you must register for A2P 10DLC.