The idea is pretty cool, but it doesn't work super well. 1. I imagine most major news outlets don't have RSS feeds these days. 2. A lot of stuff originates from news agencies, so they don't spread from website to website, but radiate out from the agency. 3. Most of the included sources are pretty small. To draw meaningful conclusions we would need infos like popularity, political leaning, nation of origin, etc. 4. The similarity check doesn't appear to do translation. So when news spreads from one country to another we loose the thread.

The devil really is always in the details.