Unless you're really interested in true crime, you may not have heard of any of the crimes outside the USA. I actually started buying books directly from Australia to find out about their murders.
Three of their unsolved ones, I don't see on list.
Wanda Beach Murders
The Beaumont Children
Bogle and Chandler
The Crawford Family Murder - They know the father did it, so technically not unsolved - really gruesome murders, he electrocuted his 3 kids and pregnant wife and then pushed their car off a cliff, thinking it would fall into the sea - but it got caught on a ledge. This happened in early 1970's - father disappeared and was never caught.
Taman Shud which did get several votes, I think could be solved with DNA. A lot of people are putting their DNA out there on (I think ancestry.com) that they might get a hit.