It does make a significant difference when you start pulling in foreign players. Merchandising takes quite a bit of a hit.
e.g Australia does not have a big player base so a lot of my players have to be imported.
I am currently coming first in my conference in a relatively active league (no bots) but with only 4/13 local players, I am actually making 6k below the average of my league for merchandising revenue. Also, I noticed that the difference in merchandising revenue between when I was actually coming 4th in my conference to when I was actually 1st was only like 1k. Thus I think merchandising is a bit heavily dependant on local born players.