Let's imagine a situation Ukraine is facing where Russia is bombing electric plants. If France/Germany built it and say controlled its operation, Poland could suddenly hear they're shutting it off for security, blacking out the country in the middle of a war. The decision making of strategic assets must lay exclusively in the country possessing them, or be built by a country without an interest in which conditions it's being used. That's only one example, multiple more security concerns are there as well.