This is my General Question : Is in United States users like to use WordPress platform ? Are they like to use paid WordPress themes and plugins or prefer free sources ?
WordPress is an open-source Blog Publishing software or Blog Tool. So don't think that People of US don't use WordPress Platform. About 12% of the total Websites you see over the Web is Powered by WordPress. It depends upon the choice. But WordPress is the best Blog tool all over the Web. Easy to use, Reliable, Easy Access. Only you need is to Pay for Hosting Service. And About the Theme, Many people use the Paid sources and many uses Premium themes.But Remember if you are going to use Paid/Premium themes then you must go for Genesis or Thesis Framework Themes.
Not only in US but most of the bloggers from different countries prefer WordPress due to many advantages. Now when it comes to using free or paid resources that depends on the webmaster.