In that case it isn't Ryanair's problem. The Norwegian flight was delayed, so Norwegian has to provide care (foods, drinks, accommodation, etc) and reroute the passengers at the first possible opportunity.
The other way around, if the Ryanair flight is delayed and the passenger misses his connection to the US, it's Ryanair that has to accommodate the affected passengers, and often also has to pay EC261/2004 of 600 euro (provided the total distance is >3500km).
I can easily see why Ryanair does want to test the concept on a small scale and I would't be surprised if they eventually back out of it. I don't really see it being worth for a carrier like Ryanair, one that already has one of the highest load factors in the industry, as well as the lowest fares.
The carrier the operates the long haul flights will benefit the most, that isn't Ryanair in this case.