I see this comment a lot but I have never seen any evidence for this. What exactly is the barrier that a tech startup faces in Europe vs US? Which regulations are in the way (and are they EU or national ones)?
There is a lot of bs thrown around e.g. GDPR is far from evil or bothersome, as well funded lobby groups have made it out to be. You don't need cookie warnings if you use cookies to log your users in, only if you sell your users out to google and other analytics companies. You are obliged to have unsubscribe links in your emails to users. You have to provide and delete data you hold on specific users if requested. From a few hundred thousand users you need a data controller which is for ally responsible to watch out for data breaches (this is just an identified person, not a full time post). What's the big deal?
Much more stifling are e.g. the processes to register a company in the country you are based in or to get a bank account, and of course Europe's language diversity shrinks the potential reach so most that want to scale do so in English and then find it convenient to have offices e.g. in the US or UK.