I have a TomTom 950 Go that came with Australian maps and the option to download one other country for free so I chose the USA maps which had to be put on a mini-SD due to their size. When I am driving in the USA, will the TomTom automatically shift to the USA maps? Can I pre-load the addresses I need before we go? I can't get the TomTom to display the USA maps when I am in Australia.