Are you now talking wages or total crew costs? In wages there are not much difference between US and European Officers. The additional cost would be mostly if crewed with US or European unlicensed crew.
A vessel crewed by European or US Officers and say a Pinoy crew would be somewhat cheaper, but not a material difference. Filipino or Indian Officers may be slightly lower paid in some cases, but many companies today does not differentiate the pay by nationality, only by ability. (Hard to believe, I know)
No the routes in question does not require US flag, US built vessels, or US mariners, therefore there are very few. There are no US flag vessel in the 10-20K TEU class of Container vessels to my knowledge)
Shipping is an international business any any attempt by this or any other US Administration to change that will meet with defeat. (Just like the trade war, if continued)
If you want your piece of the cake you have to change your ways. A second register MAY be a way to do it.