“will a house turtle die if let loose”
Yes. Yes it will. Not only will it die, it will first spread diseases to the local reptile and amphibian population that they may not be able to handle, potentially doing severe damage. Plus, it’s likely a red-eared slider or other invasive species that has a terrible tendency to do damage to the entire local ecosystem.
Do not turn your pet turtles loose, people. Find a local reptile rescue and take them the turtle, along with a donation. In a pinch, take the turtle and the tank and supplies down to your local animal shelter, also with a donation. In a really severe pinch, take your turtle to the vet and have it humanely euthanized rather than sentencing it to a slow and unpleasant death by starvation and dehydration, and possibly having an awful impact on the local turtle population.
But really, no house pet should ever be turned loose. Be responsible with your pets, people.