If you look at easyjet’s map of routes from their Basle base there is a blue line (= new route on sale but not yet operating) going across the Atlantic to an unknown destination. But on their drop down there is no route to book. Is this a fat finger from their IT dept. ahead of an official launch, perhaps just as BA launch London City to JFK? I reckon their A319s could make it westward without stopping if only because of low luggage weights.
With longer routes like London Luton LTN to Tel Aviv TLV now being operated by Easyjet, it can’t be long before the East Coast USA is within their grasp, though personally I think they would operate larger aircraft like the 787 in economy plus and super economy layout.
Privatair uses similarly sized BBJs to fly transatlantic, though as you say these are only economical due to high paying business passenger and the resultant reduced take off weights:
The new Easyjet Route is Definitely Basel to Düsseldorf. If you hover your mouse over the top of the map, the blue line appears on its own, if you click it, it takes you to the information page for Düsseldorf and given that Basel is the only destination served by Easyjet from Düsseldorf, that’s your answer.