Remember, johnpower, that on this site, you're not going to get too many who are "International Only" as you had hoped. Most on the site are well-versed or at least familiar with both styles. Depending on where we all live, one style certainly is utilized, danced and taught more than the other. For example, I agree with terence often on this site, because I know the styles he taught many years ago and I know his background. I would have to admit that the only real rumba I am comfortable in is the square form, because that is what I was taught. And I really like it.
Actually, the way I see this, you were right. More of those trained in American Smooth and Rhythm would know what the box step is, but the Int. trained dancers would certainly know what it is and be able to use it, teach it, etc. Interesting debate with your wife, but no real winner or loser in the final evaluation? Everyone who answered your first post is likely very polished in both styles, except maybe me -- I'm far more competent in American style, but familiar, "trying hard" on the Int.