I have a feeling the airline (Latam) will be canceling my flight

I would check with LATAM now. You can re book on line.
Need to go to PF ASAP before border is closed and quarantined.
Health Alert – U.S. Embassy Brasilia, Brazil (03/18/2020) 
  
Location:  Brazil

Event:  On March 14, the Department of State authorized the departure from any diplomatic or consular post in the world of US personnel and family members who have been medically determined to be at higher risk of a poor outcome if exposed to COVID-19.

The government of Brazil has implemented measures to limit the spread of COVID-19.  Effective March 17, the Brazilian Ministry of Justice announced that all people in or entering Brazil must follow medical advice regarding quarantines.  Brazil is treating failure to follow medical guidelines for quarantines as a crime.  Violators, including U.S. citizens, may be subject to confinement and fines without judicial recourse.  Visit the website of Brazilian Ministry of Justice for additional information on these new measures. 

Additionally, airlines continue to reduce international services between Brazil and the United States.  Travelers should be prepared for travel restrictions to be put into effect with little or no advance notice.  U.S. citizens who are considering returning to the United States are urged to work with their airlines to make travel arrangements while flights are still available.  Many travelers worldwidehave reported unexpected flight cancellations and limited flight availability.  If your travel has been disrupted, please contact your airline.

Effective March 16, the Embassy and its constituent posts have suspended routine consular services.  For emergency American Citizens Services, including emergency passports, email the closest U.S. Embassy or Consulate.  Note:  U.S. Consular Agencies in Manaus, Fortaleza, and Salvador do not issue same-day emergency passports.