I've been involved in a couple of campaigns within large enterprise that have encountered supplemental issues as a result of search engines not making the correct distinctions as to the country localization of content.
The most extreme cases were apparent for sites that could not technically leverage ccTLDs or local IP hosting. You effectively get content from various same language countries competing for rankings, i.e: india, canada, usa, australia, singapore...
The concern here isn't really due to the language aspects but rather duplicate content so the answer really boils down to good old content differentiation.
If your pages are in supplemental, its not the end of the day, they can still drive traffic however they are a clear indication that there is something wrong with your website (maybe technical barriers) or the content is simply deemed to be of low quality.