This is a terrible idea for several reasons:
1) Yanks don't care about the Premiership. This fixture will not change that.
2) It's a 40k stadium. It'll be a major success to get a 15k crowd to turn up. It'll feel like a morgue
3) It's a baseball stadium. As an aficianado of the struggling Major League Rugby, I can tell you that baseball stadiums are the literal worst for playing a rectangular sport in, because they have the big stands on two sides in a corner, which is normally smaller than 90 degrees (because the stadium is built for people to be looking in towards that corner). That means that the majority of seats are at a shitty angle to see a rugby game. For example, this is how NOLA fit a rugby pitch into a baseball stadium (before they folded because they had poor attendance):
I can see absolutely no benefit to this idea.
Puja