It was a couple of years ago when we were looking into it, I visited a couple of forums where ex-pats were sharing information with people thinking about moving to the US, so none were diabetes-specific and were just sharing how much their monthly copays were for doctors or hospital visits (IIRC it was in the low thousands of dollars per month for couples without pre-existing conditions), we never got as far as specific insurance providers as it wouldn't have been a job transfer and companies don't tend to share specifics with prospective employees. The amounts people were paying for their copays put us off sufficiently
I know from various sources over the years that insurance providers can be very restrictive in what they will let you have for your diabetes, for example not letting you have as many test strips as you might need or only letting you have a certain type of insulin.
Sorry if that's not very helpful, you might be better off seeing if there's a US diabetes forum to see if you can get an idea of costs, as I said it was a couple of years ago when we were looking so I can't provide any useful specific information