The wife and I travel the US by truck and have had a Verizon Air Card since they were offered on the market. Service area has improved greatly. We have many other company drivers that we talk to and the ones that complain the most have Sprint or ATT. We can go from state to state and never lose the signal.
In the W. UP service can be spotty but anywhere there is a small town, you will probobly have service.
I don't know about the USB cards but ours is a PC slot card and it has an antenna port which we use with a Wilson amp and Wilson exterior antenna.
Dog
Also it will the abilty to use Wi-Fi if you do not have it on your laptop