I did a scrape of rosters for the Big Four. Here is how the share of international players charts out over the years available:
edit: Sorry guys, I goofed on Cal. The error has been fixed and the revision has pushed the line up significantly. Of the Big Four, Cal appears to be the worst offender.
edit again: Cal is not posting accurate roster data for years 2009 through 2014. I found a copy of the 2012 Cal roster, so that is now accurate. For 2013 a roster was reconstructed from statistics tables, but for a player to appear they had to score, draw a foul, or do something stat-worthy.
The dataset not only has international and domestic, but I’ve also broken out California US and non-California US.
If there were a way to post the file, I’d be happy to do so, and if there is anything you’d like to see charted, let me know.