I can see only one solution to this
No data sent to the USA and US companies needing to open European only businesses that comply with EU laws.
You don't do that then you get no business from the EU, that will hit them where it really hurts, in the balance sheet and you can bet all those shareholders will be screaming very quickly, then the US government will find itself under massive pressure as the US recovery turns into a possible US depression....
And lets be honest the quote from Big Tech: that "We expect that a suspension of Safe Harbor will negatively impact Europe’s economy, hurt small and medium-sized enterprises, and the consumers who use their services, the most". is a load of bullshit, it will hit the biggest US tech companies in a massive way, this could easily lead to EU citizen data only being allowed in centers on EU soil and run by EU business's with no USA input other than ownership and any profits being allowed to ead home, after tax that is.
It is simply the fault of US companies boardrooms for not doing their jobs and getting contingencies into place ready for this. If I were the CEO etc I would be asking several underlings what they have done to be ready and if nothing showing them the door.