You try hard to contrive a hypothetical situation which is quite different in context.
I can see why the DoJ compels a US corporation to deliver up some of their emails not stored on US soil. It's another matter to ask Amazon to break UK laws.
No no no .. this is not hypothetical, it is fact.. The context is little different...
. If. Amazon, a US corporation, receives a request for Mr Wooshes income and expenditure, because there is an assumption that he was drug dealing, or supporting Breton freedom fighters, and the US FBI believe that this can make a case against him, they get a warrant.
Probably the DoJ requests the UK revenue for the information both as a courtesy and to expedite the investigation, which they might decline to give, on foot of your EU rights.
Their court then orders Jeff Bozos to hand it over or he goes in the clink.
That is precisely the situation where Microsoft is now in. The Redmond executives are still out of prison because the original court decisions are under appeal at the US Supreme Court. For Microsoft to have handed over the email of this person would be in breach of Irish and EU law... We may not be as large as the UK but we are fierce on defending our rights....
Just remember that the US is very concerned about anyone breaking their laws and rules and detaining their citizens, but have less interest in defending other counties laws.
And again if you believe my references to encryption as legally munitions as fanciful, I would refer you back to the birth of PGP and the case against its author Zimmerman in 1993. ... You can argue that the scenario of you being labelled a terrorist because you refuse to hand over your private key, and are therefore dealing with "munitions" as hypothetical and it is, only because the court cases are still outstanding.