Movie takes place in the USA after a nuclear war. It goes into the snow fallout and other topics. Not sure date of movie but at lease 1980s or later

There was a made for TV movie in the mid 80s called The Day After. I remember it as being a big TV event when it came out. It had a lot of famous 80s actors in it, like Steve Guttenberg, JoBeth Williams, John Lithgow...

Yes, and Jason Robards was the main character. It was set in Lawrence KS, I believe.