There is little or no influence of Napoleonic law via Louisiana on US law.
Most common law decisions originate out of local issues and local laws. If there is an important principle in US law on rights respecting, for example, Dixieland Jazz or gumbo, there is a high likelihood that it originated from Louisiana, and will have at least been influenced by Louisiana decisions from courts regularly applying Louisiana based experience.
In Canada, a significant percentage of our courts are in Quebec and regularly have to bring Quebec law considerations to the disputes that arise there. The decisions from those lower courts form much of the law, and often end up being adopted by higher courts in their decisions.
Yes, Quebec has more influence on Canadian law in general than Louisiana is likely to have on US law in general, but courts in other jurisdictions are entitled to read and adopt with approval the reasoning from those other courts.
Otherwise, I would never have had the opportunity to learn of the existence of the US appellate justice with what must be the best name ever: Justice Learned Hand!