That little girl kicked your ass.
Following the trucks from the warehouse, Sam and Bucky get into a scuffle with the Flag Smashers atop the vehicles, who they now realize are super soldiers.
Numerous behind the scene photos of this sequence show the actors atop stationary vehicles with green screens behind them. However, the roadway shots were filmed in Hampton, Georgia (just east of Atlanta Motor Speedway) on GA-20.
The production filmed on the Eastbound side of the road traveling the opposite direction from the normal flow of traffic as seen in the behind-the-scenes images below from The Making of The Falcon and The Winter Soldier on Disney+. Many visual effects were used to hide that this was filmed in America and make it look more like Germany.
In the final shot below, when John Walker stands up, the Georgia background is removed and substituted with footage outside Beroun, Czech Republic–as seen in the following scenes.
Behind the scenes view of trucks on a Georgia interstate. 
Behind the scenes view of trucks driving away from a fallen John Walker. 
Behind the scenes view of John Walker standing on interstate.
MAP
(The Falcon and The Winter Soldier S01E02, 2021)
MCU: Location Scout 