Different rules and roles for data retention, security, privacy, etc. Different languages and interfaces, completely different cultures with regards to sales, marketing, hiring, etc. Regulations -- both official and "official" -- could be very complex. Laws, taxes and accounting may be wildly different. Hiring in France or Germany, for example, is totally different beast than in the US. Very different roles for Unions, employee retention, trial periods, etc. These need to be baked into the website, otherwise you're just Craigslist in a different language -- and CL is already there.
Then there may be deep regional differences in those countries, just as how different states in the US can have all sorts of different, often subtly nuanced, laws. It's not just US law, it's California Law vs. New York Law vs. Delaware -- which means you need an accountant who can do each of those.
And then there is the offshore work, stuff that's contributing to the main efforts. QA teams in Croatia, Support in Mexico or India, etc.
The base code may be the same for those websites, and plenty of shred repos, but it isn't just hiring 2-3 locals, getting something translated, and then slapping some VMs & containers on AWS Europe and calling it a day.
