How do people solve the problem of calling cards when they travel to America?

Go to the business hall and start roaming in America.

But it is necessary to ask whether it can be used nationwide, because there are many telecom operators in the United States, and some of them cannot cover the whole country.

Then there is the need to access the Internet, then you should also consult clearly whether the opened business can access the Internet and whether the network speed is 3G or 2 G.