It and the politics that made it. It blew nuclear fuels dangers way out of proportion, and made the uninformed the disinformed. When Karen Silkwood died she was autopsied by the Los Alamos Labs with the consent of her father, they found the amount of plutonium and plutonium byproducts in her body was withing three tenths of a nanocurie of what the plant had said. Also, she died in a car accident after taken a double dose of Methaqualone (sic) and had fallen asleep at the wheel. Not the big conspiracy portrayed in the movie.
Movies like Silkwood and the China Syndrome fueled the rancor felt by the populace against nuclear power, which is a reason why a vast majority of the baseload power plants in the US are coal-fired. Baseload power plant building is a huge investment in time and money, so a lot of plants built in the last two decades have been "peak load" plants, smaller but fueled normally by fuel oil or natural gas. and are a large percentage of US oil consumption.