Since many international students apply to us universities for business, engineering and medical, does it increases chances for being admitted of international students who apply for unique subjects like Anthropology or Archaeology?
Typically no, it does not. The exception would be if you 1. Have specific skills or résumé items that support you getting in for one of those weird subjects (if it were Anthropology, for example, perhaps you had experience conducting survey research as part of a volunteer for your local hospital)
2. Have weaknesses in an area required for one of those more common majors (if it were Engineering, for example, and your grades in math were bad).
I find applying without a major specified is usually safest, although with engineering programs in particular you often can’t do that, as admission into a university’s school of engineering can be separate from normal admission.