Shouldn't Trinidad and Tobago be included as it starts with T?
"other country" = another country
less than 50,000 = fewer than 50,000
Just a quick reference on Wikipedia (yes, yes the font of all knowledge...) shows the difference between the continental Australia and the country of Australia is the inclusion of the island of New Guinea, which would also include PNG.
I note that PNG is an acceptable answer in this quiz and submit, therefore, so should Australia. We are definitely a sovereign country and would like to be included in such quizzes...
C'mon, mate - let us play too!