I think Norwegian will be cautious with the MAX intro, they will only have 6 airframes in 2017 .
Like the UK and Europe the big legacy airlines have tended to grow lazy using hub and spoke rather than point to point, there are hundred of smaller regional airports in the US that have more than enough catchment area to support a 737 long haul operation to Western Europe.
I would expect to see a lot of new routes from the US to Europe from Norwegian