RE: Winchester model 70 US made?
They are still made in the states. 1964 is the year that they changed production and design of their firearms in order to keep up with the changing times. They did away with things like hand cut checkering, hand rubbed oil finishes, expensive and time cousuming machining methods, hand fitted parts, etc... etc... This didn't happen over night but over the next couple of years the old way of doing things faded away to the more stream lined and more cost effective way of producing firearms.
Your gun may or may not be of the "pre 64" design and methods. The biggest thing to look for is the large claw extractor that sits on the side of the bolt body.