Many people suspected the US immediately, and not just quacks and randos - a Polish member of the European Parliament tweeted 'Thank you USA' in response to the act.

Tucker Carlson ran a segment speculating on whether Biden had just ordered an attack on a NATO ally not long after.

Can anyone verify it? No. This the kind of verification that governments will keep to themselves until long after the matter has ceased to be of consequence - like the cargo of the Lusitania.

The biggest indication I can see that it was indeed the USA is that Germany has been silent on the matter, despite the fact that hey have now had ample time to analyze every bit of radar, sonar, ocean and air traffic in the area.

If it was Russia, they would say so.

Conclusion? It's an ally, and one who calls the shots to such a degree that Germany will take the loss of billions of dollars of infrastructure and hundreds of billions of dollars of economic output in cowed, subordinate silence.

It can only be the USA.