fix

app/design/frontend/Joshine/breeze/Magento_Checkout/templates/onepage.phtml

@@ -106,6 +106,8 @@
         padding: 5px;
         border-radius: 3px;
         box-shadow: none;
+        width: 100%;
+        box-sizing: border-box;
     }
     select {
         background: #ffffff;