The rules make it clear it's open worldwide. They even specifically mention world regions for the Grand Prize. Furthermore, though I haven't been very lucky, I know it's honest because I won a USB 3.0 controller last year and they helped me fight some onerous customs and "administration" fees FedEx had tacked on. Trust me, I'm a contest freak and this is the best one out there year after year.
"3. Eligibility: The Contest is open to everyone who is at least 18 years of age or older at time of entry. VOID WHEREVER PROHIBITED OR RESTRICTED BY LAW. Employees (and their immediate families) of EVGA Corporation and its affiliated companies are not eligible. By participating in this Contest, entrants (a) agree to be bound by these Official Rules and by the decisions of EVGA Corporation, which are final in all matters relating to this Contest and (b) acknowledge compliance with these Official Rules."
"5. Winner Selection/Notification: Three (3) Prize Winners will be randomly chosen to win the Grand Prize referred to in Paragraph 1 (the "Grand Prize Winners"). One (1) Grand Prize Winner will be chosen from North America, Central America and South America, and one (1) of the Grand Prize Winners will be chosen from Europe, Middle East, Africa, and one (1) of the Grand Prize Winners will be chosen from Asia/Pacific Islands. All Winning Eligible Entries will be posted on the EVGA Corporation Website at http://www.evga.com/12/scavenger/ on August 4, 2011 12:00 P.M. (PST) based on the criteria set forth in Paragraph 4. All decisions related to this Contest are final. EVGA Corporation expressly reserves the right to delay the announcement of the winners for creative or technical reasons or for any other reason EVGA Corporation deems it necessary. Following the announcement of the winners, EVGA Corporation will make a maximum of two (2) attempts to reach each chosen winners via email at the email address provided on his/her online entry form. The winners will have Seven (7) days to respond and confirm participation. If a winner is, for whatever reason, unreachable or does not respond within Seven (7) days, an alternate winner may be selected based on the judging criteria set forth in Paragraphs 4, 5 and 6 from among all remaining Eligible Entries received."