Why is HA Voice Preview going to an outside IP address in San Francisco when using Local Assistant?

Yeah that is exactly why I wrote what I wrote because unless you have some privacy focussed ISP then actually you are completely wrong. Your ISP will likely be keeping records for longer and not be anyway as secure as Cloudflare as there business model is internet security and redundancy.
The Google DNS and Cisco are similar, but the worst is very likely to be your ISP.
In the UK as it varies to the country you are in but the Secretary of State can issue retention notices to ISPs, and the duration of the notice is limited to 12 months.
Google “isp hacked” before you say anything else.
As I was saying if your worried about privacy focussed public DNS then you are probably better to go offline.

Your ISP has all your data anyway, at least in theory, regardless of which DNS you are using. You using Google DNS is not protecting you from your ISP, it just gives Google even more data.

Google doesn’t use its DNS data as it has a written privacy policy, cloudflare same …
Your ISP doesn’t provide any written privacy agreement, using Google, Cloudflare or Cisco is more private than your ISP DNS and likely more secure.
Using Google click services is where they track to accounts and profiles and create all that $, Google doesn’t need DNS to make $ and can not because it has a written privacy policy very different to its other services.
If you don’t like Google just for the sake of it use Cloudflare as could even be more secure than Google apart from sniffing.
Your ISP’s generally lag behind the security infrastructure of the big guys and apart from holding your data for long legal retions, they are far more often hacked.
It just makes less of a news story when they are.
As I keep saying if you believe its a matter of privacy then go totally offline.

Actually In in Europe and ISP has to follow the GDPR, which means it can’t use the personal data except for clearly defined reasons.

But that wasn’t my point. My point is that ISP already has all the data regardless of I use their DNS or not. All my internet traffic obviously goes through the ISP, including traffic to the DNS. My ISP has all that data anyway. Not using their DNS doesn’t change much.

I’m not saying Google uses DNS to track people activity individually, but it’s extremely valuable big data for them for sure. I see no point adding my piece to their monopoly.

That is exactly it as you say it makes no difference, unless you just don’t like the companies.
If DNS is a worry as port 53 is not encrypted, you should be using a TLS or HTTPS service, if security and privacy is of any concern.
The only concern really if you just don’t like those companies and that was me just being honest amongst some comments that where just hyperbole.
Unencrypted DNS anywhere, really is bad, but no-one even mentioned that, but went straight to Google ghost stories.
I just use port 53 and Google and yeah I am aware how easy it is for anyone to sniff all the DNS traffic I am creating, as is anyone on the unencrypted port 53…

Privacy policy meh Google must coff up any records for your IP just as your ISP does, when the government orders them to.

agreed on unencrypted dns being bad.