As millions of Americans prepare to travel for the US Thanksgiving holiday on Thursday, the agency said potential attackers could target private or government interests.
The department did not advise people against travel but said US citizens should be vigilant, especially in crowded places.
The State Department has regularly issued such worldwide travel alerts since the Sept 11, 2001, attacks on the United States. A State Department official said the latest alert, which expires Feb 24, effectively updated past warnings.
In the statement on its website, the State Department said: "Current information suggests that (Islamic State), al-Qaeda, Boko Haram, and other terrorist groups continue to plan terrorist attacks in multiple regions."