Both French oak and American oak can be used to age port, however, the choice of oak will affect the final flavour profile of the port.
French oak is known for imparting delicate and nuanced flavours such as vanilla and spice. These flavours complement the fruit-forward and complex flavours of port, and can add a level of complexity to the wine. French oak is also known for being less porous, which can result in slower aging, which can be beneficial for ports that are intended to be aged for a longer period.
American oak, on the other hand, is known for imparting bold and pronounced flavours such as coconut and dill. These flavours can complement the rich and robust flavours of port, and can add a level of depth and intensity to the wine. American oak is also known for being more porous, which can result in faster aging, which can be beneficial for ports that are intended to be aged for a shorter period.
Overall, the choice between French oak or American oak for aging port will depend on the desired flavour profile and aging time. Some producers may prefer to use French oak for aging their ports for a longer period to achieve a more complex and nuanced flavour profile, while others may prefer to use American oak for aging their ports for a shorter period to achieve a more rich and robust flavour profile.