With the current situation concerning Privacy Law, being that it is becoming quite complex, what we need is a "Data Extradition Treaty"
If your Courts want some Data which is related to an ongoing investigation, you trundle over the Country that is holding it, and ask for permission to get it.
As long as the local Court has some sort of leverage over a company, they can make that company do their dirty work. The second they lose that leverage, they will have to do it themselves. The thing that the US Gov has to remember is how this could backfire. ITAR guidlines were designed to prevent the spread of military technology, then it was used to give US firms an advantage in foreign sales. Well, that has backfired now, as ITAR un-encumbered weapon systems are growing in popularity. Recently, Canada, a notable ally of the US encouraged the use of non-US systems in order to reduce risk and delays. This DATA situation seems likely to cause similar issues.
In the end, Countries won't really care about complying with US law, especially if the DATA concerned is personal data belonging to that Country's citizens. I see lots of stove-pipe systems cropping up in order to remove the likelihood of having a data-leak to the US justice system.
My 2 cents