If you'd rather just block sales to EU buyers to avoid any VAT concerns at all, you can enable Require Buyer's Shipping Address in the settings of each product, then go to Seller Admin > Manage Shipping, Tax, Discounts > Shipping Settings:
- Specify your Shipping Origin country (and ZIP code if you're in the US);
- Tick the Limit Shipping Destinations box and select every country you're willing to sell to*;
- Click Apply to save changes;
- Click Back to Admin.
- Be sure to use E-junkie Add to Cart buttons (not Buy Now buttons), as this method restricts the countries available for buyers to select in your shopping cart.
However, the above settings only limit what buyers can select in their cart before checkout, and in the checkout pages we manage for card-based direct payments. A buyer using PayPal could still cheat by selecting any other available country in the cart, then proceed to checkout with PayPal and provide their actual address there. To block countries at PayPal's end as well, please see this page for further instructions.
If you're only using PayPal Payments Standard for checkout and might consider limiting sales to US buyers only -- e.g., if you're based in the US and don't want to be subject to EU VAT -- the simplest and most effective thing you could do is simply block non-US checkouts in PayPal. To do this, log into your PayPal account and to to Profile > My Selling Tools > Block Payments > Block payments from users who: Have non-U.S. PayPal accounts (this also applies to card-based checkouts without a PayPal account on PayPal's checkout site). On that same screen, you can also block non-US shipping addresses; in this case, you should also select United States as the sole permissible Shipping Destination in Seller Admin > Manage Shipping, Tax, Discounts > Shipping Settings screen.