iPhone (IOS)

Device settings do not require any changes for international travel.

Samsung

Check if Settings > Connections > Mobile Networks > Network Mode is present.

• If not present, no action to take

• If present (older models), set network mode to Global (valid setting in the US as well)

LG

Look at Settings > Tethering and networks > Mobile Networks > System Select

• set System Select to Global (valid setting in the US as well)

Motorola & Google

Check if Settings > Network and Internet > Mobile Network > Advanced > Preferred Network Type is present.

• If not present, no action to take

• If present (older models), set Preferred Network Type to Global (valid setting in the US as well)

All other devices

Check under settings, there should be something like:

• Settings > Connections > Mobile Networks > Network Mode

Or

• Settings > Network and Internet > Mobile Network > Advanced > Preferred Network Type.

This should be set to Global.
If there is no such setting, no action needs to be taken.