EU provides trade, geopolitical weight, smooth proceeded across borders (no passport or customs checks from Poland to Portugal..), reduces friction and competit

EU provides trade, geopolitical weight, smooth proceeded across borders (no passport or customs checks from Poland to Portugal..), reduces friction and competition between the neighbours (first big policy ~60 years ago was the Common Agricultural Policy CAP, which provides common subsidy levels and avoids conflicting subsidies/races to the bottom), enables standards, builds trust in institutions across borders (from passports to taxes to the legal system), provides great trade agreement terms with third countries and visa-free travel to 50+ countries, and most of all it always was and remains a peace project.