Markets are now "de-globalizing" in real time but that is less relevant for startups. Any entity that is now a "global" multi-national had to grow into that status at some point in their lifecycle. That trajectory is much easier (depending on sector) if the starting point is within a larger country. There are multiple factors: easier access to capital, more human talent, larger customer bases, a single regulatory framework etc. etc.

These factors don't just act linearly, but in a combinatorial fashion that helps beat the genuinely low odds. Changing the world (which is what the formation of a major new enterprise effectively does) is not a trivial occurrence. Overcoming those obstacles is occasionally possible but it is very complex and costly. For the European economies the writing is on the wall.