So if there is a need for these forces, they need to be a lot more open about their operations with the government. With more oversight then even the regular troops and accountability up to CEO level of the company for actions performed by their armies.
None of that precludes that some parts of that structure to be private. You just need to have a structure that is resilient to non-compliance.
So I actually agree with you: if the United States want to use mercenaries, they should improve how they do it. But then again, there might be a way to do it that works.
I do not think this is practical or even desirable.
Instead, more and more, the US is trying to become a world government, with 6.7 billion people affected by their choices, indirectly taxed by their choices (US corps replacing local companies and transporting the profit out of the country), without any representation.
This is a very unbalanced situation, and is just asking for a revolution. Which will end up making life worse for almost everyone.
We need a fair world government if we want to do these things, and that means representation of all people.
Obviously, the US, which would lose the most from this, objects.
Or the weakness of those countries towards US that can be explained by recent history.
Until next war.
It's a gimmick to create "littler government" and circumvent the incredible beaurocracy that the military itself has helped create. It's also a jobs program and wealth distribution channel for a very specific class of people. At the end of it all, it also serves some specific military needs, in Iraq black water didn't follow the same rules of engagement that the military did and military leadership wanted that.
A regular army is supposed to go out, win a conflict ("shoot the bad guys"), go home, get decorated, enjoy pensions and glory; that's the core mission, and its core competency is (or rather should be) to get that done in the shortest possible amount of time (or even not getting engaged in the first place). A mercenary only gets paid as long as there is an ongoing conflict involving a wealthy-enough client. He's not interested in ending the conflict; thinking you can police him in seeing it some other way is just deluded.
An army that doesn't fight is a budget that is claiming to be cut, and you can see that discussion taking place in several european countries. In the United States, however, they have wars to fight, and so the army and its space is a huge industry, with one client, the US government; and if there are no wars to fight, it will quickly collapse.
There are in fact a lot of accusations that the military industry in the United States instigates action for that specific purpose. So they don't only keep alive the fire, as the mercenaries - they also push to start new ones! And I can tell you, the Army has more political force than mercenaries to do this.
In my opinion, if there are adequate mechanisms for the control of mercenaries (such as not allowing them to have more power than the public army, or the restriction to / of particular capabilities), having mercenaries in particular situations (such as people with a high degree of specialization) could be feasible.
The problem here is that they were given ample independent power with adequate supervision, again imho.