You have to take steps to prevent this.

In China, the justice system is part of the CCP and if you don’t comply, your company is gone.

Germany sure, but The US? Do you not remember the Snowden leaks at all?

Almost every company I've worked with the past several years has had a very strict No-US-Servers-Ever-policy, because people don't trusts the US government to not snoop around.

There might be a law that allows government to obtain the data if it is a matter of national security. And what is considered such a matter is up to government to decide.

Haha, good one.

But that's rare. Generally the data lives on a regional server and gets accessed by a CDN in a region near where the data will be delivered. If you're allowed to sign in from that region, then you're likely authorizing transfer of data (for the duration of that session) to that same region.

As for multi-region replication, it's often the case there are multiple regions in the same country - for example, us-east-1 and us-central-1. No jurisdictional problems to host the data in two regions in the same country, after all.

As to how you look up what region the user's data is stored in, well, you can keep a list of users and regions. Worst case, force the user to remember their region, and use separate copies of the website (and DNS) to pick a region to sign in on. For example, the same app/website, but at different country domains.

However, if any of these approaches are done, the operational complexity will be immense, and latency for requests much higher than they could have been. A lot of message passing would be required to build such an architecture, and a lot of bandwidth would get wasted, not to mention the unnecessary costs.

A simpler approach would to store core business data regionally, but peripheral data everywhere. For example, a todo app would store all user records, project lists, and other data everywhere, but the actual todos regionally. And yes this becomes infinitely complex will collaborative cross-region applications.

I don't think there are any good solutions yet to this, and governments should invest in creating better solutions before forcing to go down this route.

For example, American and EU users sharing documents and requesting comments be added. How do you manage both isolation and sharing? Do you copy such documents to both regions? Do comments live in the same region as the document, or in the region of the creating user? Do you just give up on foreign key integrity for documents, comments, and users because they could be in separate databases? If your American servers can request data out of the European region on demand (subject to business logic), are you really protecting data to the standard the law demands?

This assumes the law's purpose is to protect citizen's data and that it's not just a way to bully tech companies into submission by writing impossible to implement laws and selectively enforcing them.

Roaming access can be handled through a VPN

should the app forward the request to the EU node (and how would it know?)

You have to add a home jurisdiction field to the account.

What part of your question is the concern of a bureaucrat? We can drop a couple 9s of uptime in the name of local data primacy right? (I specifically didn't say "data privacy") :)