The distance from Luskan to the northern border of Amn is about 1300 miles, and the distance from the shore to the Anauroch is between 550 and 800 miles. Project the area onto Europe and turn it around a bit, and it looks something like this:
View attachment 267807
If you include the whole area on the Sword Coast map (all the way off to the Dalelands and the Moonsea, and as far south as Tethyr) you get a significantly bigger chunk of land, but that's not what I'd define as "the Sword Coast".
However, distance isn't everything. As the Western Heartlands (the portion of the Sword Coast south of Waterdeep) was described in 2e: It has miles and miles of miles and miles. The Sword Coast is defined by its major geographical features and by its cities, not by densely populated nations. The distance from Baldur's Gate to Waterdeep along the Trade Way is about 650 miles, or almost a month of travel, and there are pretty much no large settlements along the way. Compare this to the similar journey
from Paris to Berlin, and you'll hit major cities like Brussels, Antwerp, Rotterdam, Amsterdam, and Hanover on the way. That's because this part of the Realms is very much a "Points of light" setting, with a small number of strong settlements separated by dangerous wilderness.
I think it would be cool if D1D moved its focus somewhere else, perhaps to the Sea of Fallen Stars (assuming it keeps the Realms as a primary focus to begin with). There we have more actual nations, as well as more variety – plus, enclosed seas is great for travel and also offers lots of room for pirates and such. You still get city-states up in the Moonsea region as well as along the Dragon Coast, but you also get places like Cormyr or Rashemen – or Thay.