You only need 1550 barges to supply the entire USA.

*for one hour

OP not only fucked up conversion, but confused energy and power. Battery capacity is a measure of energy while grid usage is a measure of power.

The battery is 1MWh, not 1MW. There are 1000 MW in a GW. Therefore, two barges could contain enough charge to run a gigawatt datacenter for one hour, so you’ll need a barge to arrive every thirty minutes approximately.