Im not entirely sure, but they do have a US website and on the delivery page it does say the following:
Overseas Local Taxes
If your delivery address is outside the United Kingdom, you may have to pay import duties and taxes, which is levied once a shipment reaches your country. You must meet any additional charges for customs clearance. Please note that customs policies vary from country to country. We recommend you contact your local customs office for further information.
Please note international shipments may, from time to time, be subject to cross border inspections by customs authorities. “Express” courier shipments are more likely to be examined by local authorities, therefore increasing the chance of an additional local charge.
Countries that usually incur an additional charge when shipped by express courier to our knowledge are:
Russian Federation, Canada, Republic of China, Turkey, South Korea & Malaysia
I have a link for you to the page here
Hope that helps.
I'm sure some of the US members here have purchased a CW and will be able to tell us.