The fact that you’re asking/concerned tells me you’ll probably be ok.

I’m an American who moved to Australia for a while. I wasn’t ever pegged as an American because of my voice volume. What caught me was my smile; easy-coming with white, straight teeth exposed. I was told I could be confused for a Canadian except that I spoke too fast. Apparently, the speed-quipping Letterkenny sorts hadn’t made it to Australia yet.

Also, think about what you want by “assimilation”. You would probably enjoy getting to know an Aussie visiting the US, no? Getting to hear their perspective on the country they’re visiting? Enjoying seeing them experience our cultural quirks? Assume the same good faith of Australians. Current politics aside, Americans and Australians have a very friendly history. Just don’t be an asshole about it, continuously pointing out how everything is different/better in the US.

My weirdest, most uncomfortable repeat experience had a gendered element that you probably won’t experience but your wife might. Older (50+) dudes on several occasions took the liberty of telling me, an American woman, all about how American soldiers stationed in Australia during l WW2 “stole” all the womens’ attention. They were just so hygienic and handsome in their uniforms, the Aussie men didn’t have a chance. So yeah, some might have a weird grudge over their fathers or grandfathers going through a dry spell almost a century ago. I share this story to illustrate that people are people, same is Australia. You will neither be universally liked nor universally hated by all Australians. Most of them are decent sorts, and a few of them are massive assholes.

Don’t attempt shrimp on the barbie or baby-eating dingo jokes until you know a person very well.