I found a site that has over 1100 international competitions in their own
section. It's found at http://www.online-sweepstakes.com
With this one you go to the section called Eligibility on the left hand side of the page
(scroll down) and you'll find over 1100 international competitions. You don't need to
look at the other sections on the site as the international competitions are repeated in the
other sections where appropriate.
You can sign up for membership if you want to but you can enter competitions without being
a member. Competitions are listed by expiry date in the international section which is handy