How would a treaty solve it when the US has decided to aggressively disrespect the existing agreements?

Basically the US can’t be trusted to keep its word, so why make it easy for US companies to operate in Europe?

Or the US could adopt better privacy laws.

Mark one for another American conundrum: having so much distrust for "the man" while at the same time being completely oblivious to the amount of personal data being skimmed off their daily activities. But it's all to guarantee Freedom™ so it must be ok?

Much of the Constitution in the US was written by people who wanted corporations to do whatever they wanted and no government can intervene. You see a lot of this philosophy still living today in rulings and precedent.

Your tone implies disagreement but that's exactly what I want as part of the treaty.

or USA could just.. stop having such ridiculous law in place.

But is "Wait for a possible but incredibly unlikely series of events to occur" really a solution?

Solution to what?

The only problem that I see is that it's hard(er) for US companies to collect data about EU customers. That's hardly a problem for the EU customers; they can just buy from EU importers (if there's no equivalent EU product) or rely on EU service providers.

I don't really see a problem.

There is no different solution. The EU tried twice to build this kind of solution and EU courts have shot it down twice with the argument that in the face of no legal representation of EU citizens in the US it is not possible.

So the US needs to move here or it can not happen.

We already had two (I don't remember the order, but they were called Privacy Shield and Safe Harbour) and somehow US and US companies "forgot" to upheld their part in any meaningiful way, so there's some mistrust on the whole idea at the moment...

Both were illegal because they did not address the core issue. The EU commission (representing EU country governments) is more business driven and wants it to work, so they created Safe Harbour etc. They also drove the standard clauses which are illegal too (or better: If as an EU company you sign them, it's your responsibility to make sure the US three letter agencies do not access the data of your customers, good luck with that).

The EU parliament have the people in mind, so they don't think it works and drove the GDPR. The EU courts look at the law and see it's not possible to create contracts, so shot down Safe Harbour and Privacy Shields. The EU courts say standard clauses could work in principle, but see above.

Treaties are not necessarily worth much these days, when the next populist can just pull out unilaterally, or decide that following international law is for chumps.

Agree. That also means no new US or EU company has a chance to go across the pond. BigCos can set this up. Not so easy for a small startup.

How does this hinder an EU startup to expand to the US?

> human problem

Incompatible laws problem