This was Copola's first director credit. Sure some of the acting and music is over-the-top but it kind of adds to the creepiness. And consider the camera angles which made the movie look more expensive. Copola kept this very low budget by getting Roger Corman to allow him to use the same set and 3 of the same actors as Corman's movie "The Young Racers" by agreeing to shoot around Corman's schedule. Don't judge Copola to harshly on the editing either, because it wasn't 100% his.
Rock and Roll trivia: Tom Petty (Tom Petty and The Heartbreakers) was influenced by Louise Haloran's (actress Luana Anders) line "Especially an American girl. You can tell she's been raised on promises." Tom Petty sang "She was an American Girl, raised on promises" in his song "American Girl" which was ranked 76th on the list of "The 100 Greatest Guitar Songs of All Time" by Rolling Stone Magazine. Sorry, had to add this. I'm a Tom Petty fan.