As per C over D, if they don't need the extra transponder requirement in the US, then why here? Why one and not the other? You claim to pick a proven concept and implement and this is why you are financially successful. As everyone knows, it is obvious that the airspace system you attempted to have implemented was not the same hence why it has failed and the attempt has wasted tens of millions of dollars that could have funded more important things like, oh, I don't know, say anti terrorist measures or something..... no one like a stinking terrorist.