What? This is certainly not my experience.
I just went to news.google.com in my desktop browser, and I clicked on the World section. On the Iran sanctions/deal story, there are several sources grouped together in one card. The top source is indeed Washington post but the same card also contains coverage from Mehr News Agency (which it highlights as "From Iran"), Reuters, The Hill, RollingStone.com, NYT (highlighted as "Opinion"), NEWS.com.au, and Associated Press.
If I click on "View full coverage", I get more sources, of course.