Steffen, you are fixating on an irrelevant detail.
For the function of the box, the transmission of voice commands to the US cloud is necessary. Authorities have access to it. They now know your voice and can do whatever they want with it. They can match it, reproduce it. For what purpose? Who knows.
Even if Alexa now (or during the measurement, for example, of the blogger or yourself) only listens in when you want it to, that’s good. But that doesn’t mean it will stay that way. The microphone is there, the box is online. Under US control, possibly under third-party control in case of security vulnerabilities. See Hue lamps. As open as a barn door, unfortunately unpatchable, and nobody cares. If that’s not a problem for you, fine. For others, it is.
All devices with (permanent) online access must be patchable. Manufacturers must have patching obligations. Moreover, microphone arrays must be made detectable, just like video recordings. Sign on the front door.