They won't be inviting all 2000 at once, but do a rolling release. I do believe they are coming from the applications though, and believe that sites are being reviewed before the official invite goes out.
I did check the application form. It states “Participants of the program must be a resident of the U.S., with valid U.S. Social Security number or Tax ID”. However, the ID is not required in this form.
I don't know how your YPN earning from your blog is but the ads shown in this blog are not impressive. The ads for any topic are the same. It is a kind of static ads based on a group of fixed keywords.