Rugby League is still overlooked by much of the media because in many parts of the world, Eastern Europe, and Africa, it is still in the embryonic stages of development, thus some nations are easier to research than others. For the purposes of avoiding controversy in who does (and who as yet, doesn't play rugby league), the following list has been compiled of known participating nations, plus the varifiable sources.
http://www.rlhalloffame.org.uk/
http://www.leagueunlimited.com/team.asp?ID=International (Very knowledgeable Australian website features bona fide Eastern European RL nations including Latvia, Tatarstan, Ukraine, missed out on the UK Hall Of Fame website)
http://www.rlif.org/members/ Official International Rugby League Federation Website (100% accurate database - recently added new international paid-up affiliate countries to its database, including American Samoa, Ivory Coast, Nigeria, Senegal, Sweden, Norway, and Tuvalu)
PLEASE NOTE: -
* Any further additions, please add links here, to prove the nations are verifiable.