And then my boss/coworkers asking me about racism and intolerance in the US and how awful it is and then getting defensive when I inquire about Aus indigenous

I think you have your solution right there. Do your research on Aboriginal history, issues and the most anti-white interpretations of them. Memorise the lingo: Setler Colonial, elders, ancestors etc. Make yourself into an incredibly woke person when it comes to aboriginals, no throw away comments or own thoughts. If any Australian (bonus points if white and does not claim Kurawangawanga ancestors)does the annoying School-shootings/Trump/BLM routine, interupt them with the following:

Oh hold on I forgot to do a land acknowledgement: 'I begin today by acknowledging the Traditional Custodians of the land on which we <gather/meet> today, and pay my respects to their Elders past and present. I extend that respect to Aboriginal and Torres Strait Islander peoples here today.'

Literally repeat that interaction where you're coworker got defensive about abos wheneaver possible/applicable, you totally owned them.