The Russians sandbagged the project.
It was intended as an around the world PR tour and had made it as far as Japan after Europe, the Middle East, and Southeast Asia. It's next major tour segment was to have been in the USA but it never made it there.
The Ju-52 is not a long range plane. From Japan it could not reach to Alaska without a fueling stop, and the only place that could have made sense was in Russian Siberia, particularly the Kamchatka peninsula.
The Russians had delayed and dragged their heels about permission to transit Russian airspace and land on Russian soil to refuel. At last minute the Russians finally pronounced that they would NOT permit the Ju-52 into their airspace, citing bad memories of the German military use of that airplane against Russia in WWII as their reason for saying, "Nyet".
The plane had to turn around and retrace its steps back to Switzerland: It never made it to the USA.