If you decide to go WWOOFing in multiple countries, please be aware there is no international WWOOF membership. Internationally, the WWOOF movement is a federation of national member organisations each with an individual fee.
However, your WWOOFer profile will be one and the same across the world. This includes that your profile will display all of your reviews gathered in one country, also when contacting hosts in other countries.
More isolated hosts located in the 80+ countries without a national organisation are listed on the WWOOF Independents website, which is directly managed by the Federation of WWOOF Organizations (FoWO). As a WWOOF Independents member, you can contact hosts in any of those countries. Please visit wwoof.net for information on other WWOOF organisations around the world.