Almost impossible to tell the two species apart from a couple of samples - I used to have to put chalk marks on them to distinguish in the offcut racks. One way to tell was that American tended to be resawn with circular saws whereas European tended to be resawn with band resawn.
The colour range and grain patterns can overlap so it’s really hard to be sure… have a look at oak veneered MDF, it’s always American White oak veneer, but the colour range can be pretty broad
There is a vital difference in its make up though, American White Oak has longer and open cells which means in our damp climate it’s not a durable material externally.
Over the years I varied buying American or European for internal stuff depending on price and quality at the time. American always used to be cheaper but that changed in recent times.
