We could actually build nuclear plants fairly quickly, but we'd have to streamline licensing of course and probably focus on one design. When we build say 737s, they are all the same (for a while, then they build 737-200s etc.). If we had a standardized power reactor design, it's a matter of duplication. Once you sort out siting and funding, the rest should be easy (relatively).
It already produces 20% of our electricity with about 100 power reactors, we "COULD" double that in a decade with some significant effort. That would at least replace coal, our dirtiest fuel. We'd still have NG emissions, but it's a lot better than coal. I could get behind that plan, but it's obviously not practicable.