At least one state was left without phone access to emergency services as 911 calls stopped working.
Alaska State Troopers told local news there are extensive problems with the emergency systems.
Reports suggest other states were also impacted.
The cause for the system failure is not currently known.
Many television channels around the world have been hit by the outage, with Sky News in the UK broadcasting from a phone after its studio equipment failed.
The Paris Olympics organizing committee also said it had been hit by the outage, but that it had contingency plans in place.
