Australia should figure out which country they are from and put them in boats in international waters just outside their country of origin’s waters.
Don’t forget the oars!
End of problem.
We actually do precisely that under current policies.
Unfortunately these people were let in when the previous Labor government softened our policies. That's what created the mess.
I don't think America should take these people - it has no obligation to clean up an Australian mess - but the situation is not one the current Australian government created either. John Howard solved this issue back around 2001 - and then we got a Labor government again that didn't like being nasty - and so opened the floodgates of unlawful arrivals again.