[95th Rifleman]

there has always been friction comparing British/Commonwealth kit with American.

America has to equip a massive army economicly. as a result they have an assault rifle that essentialy works but can be mass produced relatively easily and cheaply (sure the M16 is a bit complicated but well within the capabilities of America's industrial base). When you look at some of the other American kit, it's bloody awesome. A good example is the 50 cal MG, this thing is decades old but nobdy has yet built a weapon that can replace it.
Another example is America aircraft. Both Australia and New Zealand are quite happy to use American warplanes because they are the best in the market for the required role. I often wish the British governemnt would swallow it's collective pride and replace the Tornados and Typhoons with F/A 18 Hornets like the Canadians did.

Australia has a much smaller military and can afford to be picky, hence they went with the AUG for infantry and American for air force.