Bear in mind that this is a decision of a delegate of the Commissioner of Patents. This decision won't bind anyone except, presumably, the Commissioner of Patents. Its value as a legal precedent anywhere else in the world is roughly zero.
If that is the case (a big if), I suppose there could be some legal implication in the US, but you'd have to ask a patent lawyer with intimate knowledge of the FT agreement to be sure.
The USFTA doesn't automatically mean that Australian IP decisions gain legal significance in the US, or vice versa. For this decision to actually have any impact on Amazon's patent in the US, someone would have to litigate it. The Australian decision could certainly be used as evidence in that litigation (as the questions of novelty would be similar), but as noted about would not have any binding authority.