I'm guessing they just meant last American WW1 vet then, and this guy that just died was the last WW1 vet, period. Kinda sad though, they were both 110 years old, both died within a month or two of each other.

He played his role in the history of mankind. An unwarranted death is tragic, but the long life this man lived and what he accomplished is worthy of celebration and joyful remembrance.

Rest in peace.