There is no way this would’ve be useful the cross the Atlantic or pacific oceans to invade the continental US.

The only area where this might be useful is in the Great Lakes, at that point the USSR already had to invade Canada at the least and establish a sufficient presence to support these things, and even then it’s not clear if it would be more useful than traditional transport.

These things are cool from an engineering point of view but are quite useless in real world applications.