Usage of nationwide

"The models -- which boast features such as wireless earphones and a much improved camera -- are available at retailers nationwide."

na?tion?wide /?ne???n'wa?d?, 'ne???nwa?d/ ??? adjective [usually before noun] happening or existing in every part of the country SYN countrywide a nationwide search for a missing British tourist nationwide television

—nationwide adverb We have 350 sales outlets nationwide.

http://www.ldoceonline.com/dictionary/nationwide

According to dictionaries, the word nationwide modifies nouns in front of them like nationwide television but in the example sentence, it is put behind retailers and then nationwide functions as a an adverb there?

I think that it should be an adjective to make sense.

What do you native English speaekrs think?

Thank you so much as usual in advance!