From CNN

The NRF is one of more than 200 business groups that sent a letter to the White House this week asking that the Biden administration act to prevent a strike, saying that the country relies on moving both imports and exports through these ports.

“The last thing the supply chain, companies and employees…need is a strike or other disruptions because of an ongoing labor negotiation,” said the letter.

The letter does not explicitly spell out the action sought, but it implies President Joe Biden should exercise powers under what is known as the Taft-Hartley Act to order a quick end to the strike, as President George W. Bush did when he halted an 11-day lockout of union members at West Coast ports in 2002.

Some economists think Biden will decide to take that action, despite strong union opposition to such a move.

Imports (including energy) are 15% if the US economy.
Shutting down a portion of non military imports at a portion of harbors is easy to overstate/sensationalize. (like Hurricane coverage)

But the impact would be significant, and the panic and panic bidding would be real.