I have worked extensively with multi language and Sitefinity and there are few tricks that will definitely make your life easier. I think I need more info on how you applied the localization whether through pass prefix or domain however here are some tips from my personal experience with localization and Sitefinity:
1- Use multiple themes for multiple languages, let's say you have English and Italian and each version has its own set of stylesheet files. You create two themes, one called SiteName English and the other SiteName Italian and this way each page you create will get the style sheets according to the culture because each culture has its own theme.
2- For the other set of files, let's say JS and Images, you can use the Global Resources to achieve this. Let's say on the home page of your english website you want to display MyImage_en.jpg and on the Italian home page you want to display MyImage_it.jpg. You add a resource entry to the Global Resources one called HomeImage with value MyImage_en.jpg in the English resource file and the other HomeImage with value MyImage_it.jpg in the Italian resource file and you're good to go.
3- Use Telerik.Cms.Web.UrlHelper.ResolveUrl. It is a helper method in sitefinity that gets the relative path according to the current culture and this method really saved me as before I had to code the same functionality myself.
Hope this helps.