At the end of 2005 , Speed drove the first three races of the new A1 Grand Prix series for A1 Team USA . At the end of 2005 , Speed drove the first three races of the new A1 Grand Prix series for A1 Team USA , achieving a best result of fourth in the Feature Race of the 2005 â `` 06 A1 Grand Prix of Nations , Portugal , held at the AutÃ dromo do Estoril .