Once you learn what to look for, it becomes easier to distinguish between wines aged in French versus American oak. The difference in oak has to do with how close-knit the oak’s fibers are. European oak has a more open knit and therefore must be split lengthwise to avoid leakage. The labor adds up to higher priced barrels. American oak is less porous and can be sawed. There are differences in flavors and tannic textures imparted too, with European oak lending more low-key vanilla and smoothness than American. Another thing that can change the nature of the oak is how much the inside of the barrel gets toasted.
Related Link: What’s the difference between French and American oak?