You have a confusion of terms.
The tax that a buyer pays depending on their country is called VAT.
The tax withholding is for the seller's profits and has nothing to do with the country from which the game was purchased, but rather with the country of the store.
Itch responds to the US IRS, and any transaction where you must be paid is governed by those laws.
If you don't live in the USA, and you don't want to pay taxes in the USA, you should sell through a store that has nothing to do with the USA and unfortunately, Itch, it doesn't work for you.
EDIT:
I'm not 100% sure, but I think that Itch's direct payment option allows you to continue distributing the game via Itch and have your accounting system completely independent, but I don't know if that forces you to pay US taxes or not, it is It is better that you consult with support or a local lawyer in your country to avoid any legal problems.