Porsche 928 Introduction in the USA

Thanks to 928 OC member Eric for sharing some interesting historical Porsche 928 information.We know that the 928 Porsche was first introduced at the 1977 Geneva Auto Show as a 1978 model year.  

  

But, when was it introduced in the USA?  Here is a photo provided by the PNWR historian of the 22nd Porsche Parade, July 24-30, 1977 at Sea World San Diego, CA.