LPV in the USA
Rest assured, Part 121 carriers in the US do use the RNAV approaches. Technically there isn't an 'LPV Approach' per se, but an GPS Based RNAV Approach (called the RNAV Y or X typically) flown to LPV minima. Last i read there were ~1600 plus RNAV with documented LPV minima. They are rock solid, and frankly, it's gratifying to see our tax dollars at work promoting air safety.