I'm American, and I took a road trip last month from Dallas to NYC and back (going through Arkansas, Tennessee, Virginia, Pennsylvania, and tiny bits of a few other states).
Unless I was in a city, I only had 2G signal, and in a few places I didn't even have that (but those were rare).
Edit: for reference, my carrier at the time was Simple Mobile, an MVNO of T-Mobile (I'm no longer with them anymore: I just activated Project Fi today).