Apple owns up to sending a certain amount of telemetry[0] back home, but we have no way of verifying what it is since the traffic is encrypted. It's impossible to know what data it's collecting and sending back, or even how anonymized that information is. On top of that, Siri invocations are recorded and saved for 6 months, and then retained for an additional 2 years after being dis-associated with your account. Once again, there is no way for us to verify Apple's claims here; we could definitely have another iMessage scenario on our hands where they just keep all that data anyways, and when they're called out on it they simply blame the USA and try to look as powerless as possible. Like the other commenter suggested, it hinges solely on how much you trust a single company. This single company in question is located in the domestic United States, is known to comply with intelligence agencies, and has every reason in the world to kiss up to American authority. I'll let you do the math here.
[0] https://www.cnet.com/home/smart-home/homepod-echo-google-hom...