In Australia the speed of light actually matters for the distances light needs to travel - this is probably the same for mid-west towns not near an AWS centre too (not sure of their presence there, but I expect they are predominately on the coasts).
The speed of light is 300,000 kms per second.
Distance wise: Perth to Sydney approx 4,000kms or 13ms travel time, and Brisbane to Sydney approx 1,000kms or 3ms travel time.
I'd say it is highly doubtful to get sub 10ms from Brisbane to Sydney if you're going via even just a handful of routers. And Perth to Sydney? Forget it!
The standard deviation of any ping test I do is at least 3ms due to how DOCSIS works, and I can't ping my next door neighbor (same ISP) through the internet in under 16ms. I've done traceroutes against several servers that are in the same city as I am in North Carolina and the only one where my traffic didn't first go to Atlanta or DC (or both) was to a server hosted by an ISP that has no physical presence outside of North Carolina. My cable modem and my ISP's CMTS each have out of control bufferbloat that adds hundreds of milliseconds of latency under load in each direction, which can't be entirely mitigated by my router's traffic shaping and AQM. There's little reason to believe that they've got got any AQM further upstream given the large latency spikes I see even when my last-mile link is quiet. Disregard for latency is pervasive in the design of the ISP's network.