To generalize: Freedom is inefficient.
Those 50 different states could all collaborate on a single enforcement agency. The difference is that they control it, instead of having it control them. They're free to leave the group even if it's inefficient and costs them. The choice is theirs to make.
This really comes down to a matter of authority. You believe that, to be efficient, it must be top down. I disagree on the importance of the top down model.
Pipelines cross various countries all the time, those countries don't need being dictated to by a higher authority. Why do they keep their freedoms but not Americans?
Anyways... a collaborative effort CAN produce the same national agency that you aspire you create, it's just a question of its authority. To fight the top down model and encourage state's rights we can make the most of the power of the minority in the Federal government to block everything.
There's a reason businesses, governments, and pretty much every successful organization runs on a top down model. In a capitalistic society inefficient organizations will die out.
Also, you cannot possibly compare situations with sovereign countries, each with their own political, economic, and military systems to this one involving US states. It's even possible that those countries have their own national standard for gas pipes or have corroborated to come up with one. The difference is that serious consequences such as wars, political ramifications, trade sanctions, or other serious consequences happen if one country decides to screw up.
It's not really about control, it's about
liability and responsibility. Who is going to responsible or liable if another state decides not to participate and your state depends on a pipe in their jurisdiction? Are you going to build a separate pipe that goes around that state just to deal with that?
If you have 50 states that collaborate on a single enforcement agency then why would a state even decide to give authority to that agency if they could just walk out and decide to screw everyone else? How useful would that kind of agency even be? It's like the IAEA with its inspectors. If countries like IRAN don't want inspectors then they don't need to have them.
Besides, how will that enforcement agency be any different than a single federal agency, except without any authority? Congress appropriates money to these agencies anyway so in essence they are representing the people and states for these agencies.