I don't think the previous answer was correct. I think mainland China is far bigger than the United States. The order would probably be: Russia, Brazil, China, Canada, the US then Australia. I'm an Aussie and know US to be just marginally larger than Australia, being roughly was wide and same distance from north to south.
After that it gets a bit tricky. Probably Argentina then India and then a swag of Asian and African countries. Note, I do not include Alaska as part of the US here. If so, then it would be quite a bit bigger than Australia.