Hey There!
I activated the $60 plan today and i've taken a couple screen shots for you. Doesn't look like US Data is mentioned. On that note a couple things you could try.
First. Power off your Phone and Back On. When you switch on to a different carrier, sometimes the APN (Internet stuff on the network side) isn't always pushed to your phone.
If that doesn't work, I would suggest manually selecting AT&T or T-Mobile as the other person mentioned. This in theory should force the APN settings on to your phone.
If you are still stuck, the only other thing I can suggest is to Call Public in the AM - or chat online 
private message while on WiFi (because LTE/3G isn't working) to see if something is stuck on the backend.
There isn't a whole lot more I can think of trying out at the moment. I mean you could try to manually enter the APN for AT&T or T-Mobile however if you aren't 'advanced' to some degree then it may be a bit tough. If you do go that route, just Google "AT&T APN Settings" or "T-Mobile APN Settings".
Where you enter the information varies by phone, but a quick search should put you in the right direction. I don't believe iPhone users can manually enter this information....
Let us know how you make out! Enjoy your trip 🙂
