An Ethiopian Airlines plane en route from Addis Ababa to Nairobi crashed six minutes after take-off on Sunday, killing all 157 people on board.
The incident followed Lion Air 737 Max 8 crash in October that killed 189.
Some in the aviation community have called for the aircraft to be grounded pending a full investigation.
But late on Monday, the Federal Aviation Administration (FAA) issued a "continued airworthiness notification" saying the plane was safe to fly.
China, Indonesia, and Ethiopia on Monday ordered their airlines to ground the jet. Other airlines kept flying the 737 Max 8 after Boeing said it was safe.
Shares in Boeing fell by 12.9% on Monday in the wake of the crash.
US Transportation Secretary Elaine Chao said the FAA would "take immediate and appropriate action" if a defect was found in the plane.
FAA chief Dan Elwell said the notification "informs the international community where we are and (gives) ... one answer to the whole community".
Paul Hudson, the president of FlyersRights.org and a member of the FAA Aviation Rulemaking Advisory Committee, called for the plane to be grounded.
"The FAA's 'wait and see' attitude risks lives as well as the safety reputation of the US aviation industry," Mr Hudson said in a statement on Monday.