There are all kinds of CDC websites that address this 'kind' of thing but much of it boils down to SHOULD do this, that or the other thing related to isolation and travel. If you test positive prior to arrival in Bermuda (let's not debate whether this is strictly required by Bermuda... that's a different topic), you'll likely be put in isolation immediately and will probably spend enough time there that the ship's medical team can give you, hopefully, a clean bill of health prior to disembarking in the US. If you're not cleared (and don't need additional medical assistance) by the time you get to the US, the guidance is for you to isolate further. Now, this is where it comes down to your own personal convictions on travel... you can isolate for a few more days or you can spin a little story to get on the airplane without knowing your exact status. Whether your passport is flagged by US CBP upon arrival in the US, I don't know.... that would be a complicated administrative matter. Have a look at this and keep clicking on links until you get an answer you like, then stop looking.
https://www.cdc.gov/coronavirus/2019-ncov/travelers/index.html#can-i-travel