If there is one American player in today's NHL who has a case, it is Patrick Kane. Three Cups, Hart, Art Ross, Calder, Smythe, three times in the first all-star team and so on. What's more, he's a career PPG player - in 769 games.
So, if Matthews wants to be in the discussion, having a career superior to Kane (who, by the way, is a lock for the HHOF) would be a start. Then you could factor in the other all-time American greats, and you would quickly realize how f***ing far away Matthews is from being any kind of legend worthy of "best of all time at X" mentions.