HN is very well known to a subset of the high-tech community, not necessarily limited to the SF Bay Area by any means, but probably concentrated there. It is less well known outside of that region, and generally unheard of outside the tech industry.
I would not expect an HN username to do much good on a resume unless, as JM suggests, you are applying to a YC-backed company.
On the flipside, the kind of company that considers your HN username a compelling data point on your resume is probably a fun company to work for. :)