The address of the user is sent to paypal unless you changed the "no address"/"address override" options of the paypal plugin so the user should not have to fill his address on PayPal.
Also, you should use the hikashop registration page and not the joomla one. That way, the address will be asked directly during the registration and the address will already be selected on the checkout when the user buys something. You can create a link to the registration by creating a new menu item of the type hikashop user registration via the joomla menu manager.
If you set the zone texas to your tax rule, of course, the tax is removed when the user is not in texas. You could set the USA instead as zone of your tax rule and the tax would apply to all people in the USA.
I don't think that you have to charge for taxes outside the USA.