Figures look entirely believable to me, though I was unaware Australia had improved so much.
The state of broadband in the US is atrocious. Geography is certainly an issue, but I blame anti-competitive practices by telecoms and the hold they have over the FCC for most of it. ISPs are largely geographically segregated by collusion and only bother to fight each other when the population densities get extreme (meaning minimal infrastructure costs and enormous profit margins). By setting the definition of broadband at comically low connection speeds, and the definition of competition that is often nothing of the sort, current regulations strongly discourage effective competition for most areas. Without competition, there is little incentive to provide acceptable service, let alone improve or expand coverage. Only in fairly dense metropolitan areas or their immediate vicinity are there likely to be enough providers for there to be any real choice. In these areas, ISPs still make money hand over fist, even while charging half the price and offering ten or twenty times the speed that smaller suburban or almost any rural area can get.
Over the last fifteen years I've lived all over the eastern and Midwest US. The fastest and cheapest connection I've ever had was about five years ago when I was living in low-income housing in the Newark area...a 75Mbps symmetric fiber connection through Verizon FiOS for 40 dollars a month. Today, as a home owner in a fairly well off neighborhood in western NY I pay almost 70 dollars a month for a 20 up/400 down (much worse than 75/75 for my uses) cable connection through Spectrum, which is the only non DSL provider that can reach me and the second highest connection speed I can get at any price, if I don't want to pay to have all the infrastructure built for something better and western NY with it's one or two mediocre options, is way better off than much of the States.
I was recently back in north Wisconsin for the holidays, and my in-laws have the fastest landline connection that exists in their area (maybe twenty miles outside Green Bay)...a DSL connection that's advertised as up to 40 megabit (if you happen to live within spitting distance of an exchange), but which normally hovers around a single megabit up and maybe five megabits down. This is a household with two working professionals in an area with one of the lowest costs of living in the country, and they cannot get an internet connection fast enough to reliably stream Netflix or update Windows.
As it stands, in the last twenty years, my average internet connection speed has barely kept up with the pace of inflation. I had ten megabit cable at the turn of the century (my first taste of broadband, and an enormous jump from dial-up), less than a hundred miles from where I've semi-settled today. Now, I still have connection speeds in the same order of magnitude, and some of the places I've lived cannot get what I had nearly twenty years ago.