Historically, Americans represented the majority of web publishers and users. This is rapidly changing as more Europeans, Asians and others get online.
When building commercial websites, it is important to think globally. Always remember that many of your visitors won't be proficient with the English language and won't necessarily your culture or values. What can you offer them? How can you differentiate your site from those of your competitors?
There are a many web tools available to translate web pages from one language to another. Although the translations are often not elegant, they can provide a good "first cut" translation that can subsequently be cleaned up by someone proficient with the language. If you publish a few key web pages in foreign languages, they will be indexed by search engines using the foreign language terms. This will bring you additional traffic.
An alternative to creating foreign language pages is to use web-based software that translate pages from one language to another in realtime.