Do health insurance companies in the US cover people all over the US?

Or is that that there are certain companies for certain cities/state? How much does an adult have to pay averagely for health insurance?
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Some plans like Aetna and United Healthcare are nationwide. Blue Cross Blue Shield has variations in all 50 states. Some plans are regional or state-specific. I don't know of any that go as specific as city. As far as an average price - impossible to answer accurately. There's too many factors in determining price - such as type of coverage, location, and business or individual, and if the employer picks up part of or all of the tab. I'm going to guess, based on my experience, that a single adult pays about $500-$1000 a month. My plan is $450 a month for just me. My parents pay about $700 a month for just the two of them. I know someone who pays $3500 a month for their family of six.
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