Building a site like LinkedIn is really easy. Europe can easily do this. All it is is yet another social media site of which there are tons. There is nothing special about LinkedIn.

The reason we didn't was critical mass. Everyone was already on linkedin and there wasn't really a reason to pick something else until the US started becoming a nuisance. It's marketing, not technical.

I'm sure an EU alternative will come up now that the US is no longer a trustworthy partner. A lot of people like myself now have ethical issues with using american products (especially from big tech) and there's a lot of demand for EU-local stuff that wasn't there before.