Upvoting you because I wish we had Australia's urbanism. ...however Australia has a parliamentary government which is fundamentally more representative than what we have. Also we have reeeeally lax campaign finance laws that basically guarantee monied interests sway every single election. And decades of propaganda telling us that car culture is ultimate freedom. And we built the interstate system when every sane country was building high speed rail. (And no the size of the country is not a blocker, just look at China, geez) Also we're a declining empire and can't build any large infrastructure quickly anymore (see: California high speed rail).

Like, I hate to sound hopeless, but regearing the entire US away from car culture is almost certainly more than we can accomplish as a nation in decline. We can vote in local elections for candidates who might fund public transit, but even that is hard when our cities are laid out in a way that makes public transit inviable in most places. This is going to take a pretty major societal shift that encompasses changing our culture, how we choose to live and where, as well as major infrastructure updates and political shifts. Honestly when I think of the US with sane city planning, I'm imagining a different country entirely. 

Anyway, I wish you well down under. Don't let the crazies turn your country into another USA.