We're isolating/quarantining now - arrived in Boston on Sunday, drove the rest of the way to our destination to avoid public transit/another flight. We had planned to voluntarily quarantine, so we stopped on the way and ran in a shop and got an ice chest, because hotel mini-fridges are notorious for not actually keeping anything cold. (Turned out to be a good choice.) Also some frozen breakfast stuff, since although our hotel said it came with a breakfast we knew most of the hotels had stopped serving and only had minimal food available. For us, they have a granola bar, coffee, an apple, and a pastry every morning. Not good for anyone with blood sugar issues. We were hoping to have food sent in, but most of the local restaurants are either not delivering now or have gone out of business. We can get Pizza Hut sent in, though.
I was able to arrange with a grocery store to send us groceries, which will arrive later today. As we have a microwave and ice, we will be fine. The hotel had upgraded us to a suite, so we have a little living room and a little kitchenette, a desk and couch, a lovely view and a huge TV.
And the most gloriously productive air-conditioning unit on the planet.
So we were planning to quarantine anyway as it was recommended, but yesterday evening got a call from the State's track-and-trace making it a requirement. There is absolutely nothing online that I found (after a month of searching) that indicated we'd be under mandatory quarantine. There's a lot about people coming in from "hot" states having that requirement, but nothing about foreign travelers. (Although it's completely logical.) When we flew in we were given a CDC sheet to fill in that asked if we had been in any of several listed countries (the UK being on that list), and our contact info, so that is, I believe where the trigger was. In my email later I found a legal/dept of health formal order that prevents us from leaving our room.
Aside from cutting us off from the coffee in the lobby and being able to walk across the street to collect online-ordered burgers (which we weren't planning to do regularly), the order has changed nothing. Except that I picked this hotel because it was in a low-density zone, a business park where there was plenty of space to walk outside for exercise with the prospect of meeting anyone as almost nil. Too bad, it looks lovely out there, but it's only for another 10 days and then we are free.
To the OP - the CDC recommends voluntary 14 day quarantines for overseas visitors to the USA. It's up to the individual states as to what they will mandate. I am willing to bet that you'll get slapped with an order if you visit. California is having a really rough time of it right now. The state I'm in has pretty much got it beat back (one of the reasons we came here), but they are incredibly vigilant. It is, really, a kind of life-and-death thing, and should not be trifled with.
It's nice, though. They will call us daily, and if we need anything (food, cleaning supplies, etc.) they said they will arrange for us to get it. We just have to ask for it. Everyone we met here has been absolutely wonderful, so far. I don't remember America as being this friendly!