According to Instagram’s CEO, the reason that Threads isn’t available in the EU is due to concerns about the upcoming data privacy legislation. European countries are poised to introduce the Digital Markets Act, which would require interoperability between competing messaging apps. Meta is also worried about the Digital Services Act, which forces tech giants to reveal who paid for the ads users see, ban dark patterns, and explain why you’re shown certain content.
Naturally, these laws present a real headache for  advertising-driven, algorithmic platforms like Threads. Still, Europeans can expect Threads to arrive at some point, it’ll just take longer. In the meantime, you can bypass the platform’s region blocking by using a VPN or changing your Google Play region.