Because we aren't actually that similar? Not that I blame you, a bunch of my own countrypeople are convinced of the same thing. In my opinion, Australia is the example of what the US could be with actual election laws:

1. We have Instant Runoff Voting (ranked choice). I'm in my late 20s and have never voted for a major party, without messing up my own future.
2. We have mandatory voting. We can argue about whether that's good or not, but the important outcome is that the government is obligated to make voting easy.
3. We have a fully independent federal Electoral Commission. It is against the law to be influenced by a political bias in your job if you work there, or to be a current party member.
4. When they redraw electorates, they must try to get them as close to a "0% swing" as they can, while following other rules around them being usual shapes.
5. Electorates are redrawn when they hit a standard deviation from the mean population.
6. Unions were never crushed in the same way here. They hold a decent amount of power in the political process, as the major left wing party gets the majority of their funding from union donations.
7. We have strict campaign funding rules.
8. The right-wing can't even elect one party to government. They're a permanent coalition between two right-wing parties. They are constantly infighting. When in Government, the larger party's leader is Prime Minister, and the smaller party's leader is Deputy Prime Minister, always playing second fiddle.
9. We have elections of the full house and half the senate every three years. That means the entire senate are up for election every six years, instead of eight. We have 76 Senators across a much smaller population.
10. Neither of the major parties has had a majority in the senate in over a decade. The current government holds 25 seats while the crossbench is composed of 20 seats, including 11 Greens senators.

So yeah, our politicians do get up on their soapbox and bluster on a lot like your politicians. But the will of the people is much closer to reality here, and there are no undecided voters. And when you threaten popular things like universal healthcare, or ignore 65% of the population approving of gay marriage, you tend to lose elections. Hell, our right wing party tried some of the transphobic rhetoric at the last election and they're now in Opposition...

I do want to strongly note, that my country is FAR from perfect. Even the US has treaties with it's indigenous populations, which enjoy some level of self-government. Australia still does not. Progress slows down here, and it takes steps backwards at times. However, we aren't exactly goose-stepping our way back to the 1950s like y'all are.