I am an American citizen residing in the UK under a biometric residence permit. My husband is a UK citizen and I have a national insurance number. Wondering if i need a special type of travel insurance to visit the US for a week or if any company will cover me?
I don't think any form of health insurance coverage is legally required to enter the US as a US citizen or, in most cases, as an alien so you don't absolutely need anything special.
The NHS has some information on healthcare abroad and a list of countries with which it has an agreement but, unsurprisingly given the local healthcare system, the US is not one of them. This means that if you want to be covered, you will need a private travel insurance policy. Since you are a resident, I think most UK-based travel insurance should cover you as well but reading the fine print is always a good idea (see comments).