You contracted with itch to sell your games in their store. Their store is located in the US. Your sales are subject to US sales laws, including tax laws.
Paying taxes is not "theft." Paying taxes in a country that's not where you live is not "theft" if you're doing business in that country. You're selling on a US website; you are doing business in the US. It is possible the tax cut would happen regardless of who buys the games, because the sales are going through a US business.
Itch may have a way for you to have your games displayed in their store, but sold by some other processor. (But probably not. Itch wants their cut for hosting the files and making them available via search.)
Itch probably does not have a way to restrict buyers by country (or IP address, or email domain name, or anything else). Part of why not, is that anyone could be using a VPN; there's no way to confirm whether a buyer lives in a particular country.
There may be an issue with your account, where too much is being withdrawn; you'll need to contact the support team to make sure your settings are correct. But other than that - if you don't want to pay US and European taxes, you will probably need to find a store that isn't operating in the US and Europe.