Why uwb doesn’t work in Argentina?? I have airtags and they are useless

This is a user to user only forum. No one from Apple is here. Since none of us work for Apple no one here could possibly answer why Ultra Wideband is not available in Argentina. All we can tell you is it isn't.

Clearly noted in the Related Article from the top of this page is the following:

Ultra Wideband isn't available in all countries or regions and is subject to international regulatory requirements that require it to be turned off in certain locations. You should ask your government why they don't allow UWB. Apple has NOTHING to do with governmental regulations in Argentina at all.

No one here could possible know or answer how Samsung is circumventing local laws. You can rest assured however, that if something is not permitted by law, Apple will not break the law.