Even when buying digital goods that require no shipping and no real contact with the buyer, people will still try to find more details about a company to be sure that it is not a scam. Some of the information they would like to know are the company contact options, mailing address, etc. If you are not based in US they will notice that very fast and they will be less interested in buying.
The reason is obvious that they trust more a USA based company. Running an USA company from outside it is hard and very costly ( 500-1000$ a month ). Most online marketers and webmasters don’t have that much money to spend, but even if you don’t have a USA based company, you can have an USA mailing address. Using a service like USA2ME, you can have a real USA mailing address and have all your mail scanned and delivered to your email inbox.
Disclosure: Some of the links in this post are "affiliate links." This means if you click on the link and purchase the item, I will receive an affiliate commission