Striking workers in the territory, which is administered as a region of France, have set up barricades on several roads and forced the postponement of an Ariane rocket.
The State Department warned of "widespread protests throughout French Guiana and along the roads leading to the neighboring countries of Suriname and Brazil."
The US embassy in neighboring Suriname can only provide limited assistance to travelers, it said, and added: "US citizens should avoid travel to French Guyana at this time.
On Thursday, the Guiana Space Center, a French and European launch site near Kourou, cancelled the planned launch of an Ariane 5 rocket carrying a Brazilian telecoms satellite.
Workers in several sectors, including the energy giant EDF and public hospitals, have launched protests this week demanding pay raises and improved public safety and health coverage.