Navigation, maps, reservations, without internet you can't do much on the road. Fortunately, mobile internet in the USA is simple and usually cheap.
eSIM or prepaid
The most convenient option today is an eSIM, which you load onto your phone before the trip and activate on your arrival day. Alternatively, you can get a prepaid SIM from one of the major carriers, often with a generous or unlimited data allowance for a few weeks. Which plan is currently the best fit changes constantly, so compare shortly before you leave.
Network coverage in nature
In cities and along the highways, coverage is good. In remote national parks, canyons, and on desert stretches you often have no signal. Download the maps for the region offline beforehand, so you can find your way even without a connection.
Using Wi-Fi
Hotels, cafes, and many restaurants offer free Wi-Fi. For online banking and sensitive logins, however, open Wi-Fi is risky; when in doubt, use the mobile network instead.
Check roaming
Some German plans include USA roaming or offer it as a day pass. That can be worthwhile for short trips, but for longer ones it is usually more expensive than a local solution.
