To do this you may need to add the item you want to buy to the shopping cart on the website and then proceed to checkout. Some shops will tell you the shipping cost by just entering the zip code (use the test address zip code of 97220). Unfortunately, many stores require that you enter all your billing and delivery details before providing you with the shipping cost. If this information is required then use the following test address and name. This is a fake address - DO NOT SHIP ANYTHING HERE:
1850 NE 92nd Ave
Portland OR 97220
In addition, some stores also demand that you give them your credit card details before they will tell you how much the shipping will cost. In most cases you can just use the following test Visa number 4111 1111 1111 1111, Expiry 10/19, CVC 789. Unfortunately with some stores this dummy Visa number does not work.
If you can't work out the USA shipping cost then just submit the order without it and my US partner will place your order using the cheapest USA shipping method possible.