Are we sure of that? It seems that US fee-paying club members would either (a) be in Europe infrequently, (b) be upgraded anyway if they fly often enough, and/or (c) be right in the midst of the upgrade game (on other than DL), and might be thought to be deserving of a seat in the club while it works itself out. US users will tend to be in the clubs when the flights leave for the US and not throughout the day.

Sure, it is an extra burden, but there are also the reciprocal priveleges for the foreign carrier to think about getting its people while in the US.

I have seen some one-off reciprocal sorts of deals anyway--Cathay Pacific hosting me in Manchester for a DL flight home, and an unnamed private club for DL passengers in Panama City (Panama)--they even went out and cleared immigration for my family while we sipped orange juice! Or the old "Flying Colonel" access privelege at Zurich on Swissair, the only sign-printed benefit for that program I ever saw anywhere in the world.

Yet Delta still lacks a proper Crown Room--or some sort of room with "Crown Room" access rights--in Paris of all places.