You realize what you're asking for is a more easily corruptible and far more powerful version of Shield right? No, governments are too corrupt and ineffective to be trusted with something like this. People keep trying to say Sokovia and New York would have been better with them supervised when that's just not true. With New York the Superheros would have been tasked with setting up a perimeter outside of the blast radius of the Nuke, in Sokovia they wouldn't even be there because they would either be in lockdown or still answering questions as to why they let Stark create Ultron.