Since I'm in the United States, I made some heavy changes to the core of SilverStripe and the Ecommerce module. In Silverstripe, I changed practically all references of Surname to Last name. In the Ecommerce module, I added support for State and Zip Codes. Linked are the results of my work. Thanks!
[url=http://dev.spearia.com/~samueloltz/silverstripe-US.zip]US-customized Silverstripe w/ Ecommerce[/url]