I have setup Paypal Express and that works fine if I create an order for Germany (Merchant Country) and some other countries.
But if I select United States in step "2. Billing Information" I get a wrong redirected after step "5. Payment Information". Instead of Paypal I get redirected to /checkout/cart.
/var/log/exception.log i found:
exception 'Mage_Core_Exception' with message 'PayPal NVP gateway errors: The field Shipping Address State is required (#10729: Shipping Address State Empty). Correlation ID: 15fb525b60ff5. Version: 72.0.' in htdocs/app/Mage.php:579