I'm not sure how you rationalise that with the fact that Australia consistently votes in a right-wing government. UK (which doesn't have compulsory voting) also reelected a right-wing government.
The "wings" are not very comparable between countries. They are influenced by their environment. I can confidently say that an alternate universe where those countries had US-style elections would have very different parties, though not necessarily more US-like.
They were talking about the US specifically.
Australia has 83%+ (with 67% being of British ancestry) and UK has 86% white population while US has 60% non-hispanic white population (with no such single major ancestry inside it like the British ancestry of the AU and UK white populations). Thus there are huge sources of racist/xenophobic voting power drivers that the right-wings in AU and UK can tap into while doing so in US causes blowback of similar scale and which grows with voting participation increase.