The Federal Aviation Administration had previously held out while many countries banned the aircraft from flying over their airspace.
But it said on Wednesday it was suspending the aircraft after analysing new data gathered at the crash site.
Boeing will suspend the entire 371-strong fleet of 737 Max planes.
The US is the last country to suspend the aircraft following the disaster.
The crash on Sunday in Addis Ababa killed 157 people.
It was the second fatal Max 8 disaster in five month after one crashed over Indonesia in October, killing 189 people.
The FAA said new evidence from the crash site in Ethiopia "together with newly refined satellite data available to FAA this morning", led to the decision to ground the planes.
It added: "The grounding will remain in effect pending further investigation, including examination of information from the aircraft's flight data recorders and cockpit voice recorders."
Boeing said on Wednesday that it had decided to temporarily ground the planes "out of an abundance of caution and in order to reassure the flying public of the aircraft's safety".
American Airlines said 24 of its aircraft would be affected by the suspension, adding: "Our teams will be working to rebook customers as quickly as possible, and we apologize for any inconvenience."