The Neoliner Origin cruises at 11 kts (20Km/h). "Straight line" on Google Earth from Saint-Nazaire to NY is about 5300 Km, so it crosses the Atlantic in 18 days.
The Emma Maersk (which I am aware plies a different route, but just for comparison's sake) cruises at 25kts (46Km/h) and therefore takes about 5 days.
The logistical chain is long, so delaying one link breaks the whole chain, and that's costly.
Same thing with train carts that arrive to pick up the containers -- there's little place to park them to wait.
If we'd only carry modern LiFePO4 at 150 Wh/kg, their range (at zero remaining payload) would be: Emma: 13300 km E-Actros: 3000 km
Thus while a substantial payload mass fraction, the heavy engine could be mostly avoided (the Emma's main engine has a specific power of about 34 W/kg; contemporary power-dense electric motors/generators around even just 1 MW are slightly above 10kW/kg; a factor of 300).
IMO rather look at whether the approach to battery packs of Form Energy allows for this level of specific energy, and if so, how to hook container crane swapped battery packs to the ship's electrics. If that's too heavy, see how such a ship could be plugged in while in port with 1000 contemporary E-Actros worth of charging power (400 MW instead of 400 kW; gives 1 day recharge after 5 days at sea). By the time that's solved, batteries have gottwn cheaper. Those 5 days of battery capacity would cost in the high triple digit million USD today; for comparison, the Emma build cost inflation-adjusted around 233 million USD today.
A container train on flat track in Europe seems to be rated to 0.15 J/(kgm) while being grid powered, over twice as fast as the Emma (also faster then the truck), though that consumption is what the traction system needs to be rated to to reliably make the train schedule; fleet efficiency should be much better.
Sadly there's oceans either side of north America unless you want to take a great circle through Alaska and Siberia or through Greenland and Norway.