- John last saw Alice when she moved to the USA.
Did they meet each other in the USA or outside the USA, please?
IMO, that would depend on when he happened to be the last time she saw her. If he was in her country, then they met outside the USA. If he was in the USA, then they met in the USA.
As you se, context matters. Please provide more context next time. It'll make things easier for all of us.
Please be aware that I'm neither a native English speaker nor a teacher.