the modern ways of radio com in the usa is probably due to an evolution...more planes on the radio, more complicated clearances and the like.
mind you I am one of the by the book guys on the radio, I still say WILCO for example (check the AIM pilot controller glossary). I say FIFE instead of FIVE and NINER instead of NINE and WUN instead of ONE.
when I was a copilot some captains told me to knock it off...but when I made captain I did it the right way.
I've heard people read back a clearance like: fl250, heading 250, 132.4 and not read their callsign. of course the wrong plane got it.
I had a japanese controller address an alpa conference and tell us all he didn't understand when a plane called for fire engines to standby...the thought that others don't call fire engines , fire engines is bothersome, but we must work together.
and the speed of speech is obviously above mach 1.0 in certain environments like LGA and ORD.
And slow flight at MACON TRACON.
But, we are still the best.
I recall flying in mexico from mexico city to san diego. We made position reports as it was non radar much of the way and I read off my position report in PTATEN fashion...the mexican controller just responded with the last two letters of my call sign...ROMEO PAPA...that was it...He didn't say who he was, or that he heard anything, he just said the last two letters of my N number.
When in Rome, be a roman candle
When in Rome, do as the romans do
When in the USA, do like the Americans do.