Content Deployment : The URL "Style Library/en-us" is invalid
I came across this error yesterday while testing a Content Deployment for a customer and had this error "The URL "Style Library/en-US" is invalid ..." with the stack trace mentioning that it was updating a File or Folder. The kind of message where you say "yeah I know, I'm deploying this so you should bring it up!".
I couldn't find what was causing the issue. For a recap, when you use first use Content Deployment (for a Publishing Site), your destination must be a "Blank Site" of the same language than the source's site collection language. However, a coworker mentioned to me another issue he had with content deployment and the solution was to add another step prior to the first deployment :
For a successful Publishing Content deployment, your destination must have first created a Publishing Site collection, deleted it, and then created the Blank Site. That will add elements to the Web Application and your Content Deployment will complete successfully after that.
I had heard of issues where Resource files weren't fully brought by the Content Deployment, that would also fix it.