In all fairness, there is very little difference between the onboard product of Norwegian and the US carriers when flying in economy class from Edinburgh to New York.
Both Norwegian and US carriers have the same seat pitch and seat width in economy class.
Both Norwegian and US carriers have free IFE - US carriers' is accessed via seat-back TVs, Norwegian's via your mobile device.
Only Norwegian offers free onboard wi-fi.
Norwegian charges for meals, whereas US carriers provide free meals.
The main difference between flying economy class on Norwegian or one of the US carriers is the arrival airport in the US, because the onboard product is almost identical.