Yea I was aware of them considering the AW101 for the Sea King, but initially it was on the higher cost side.
So, one idea (according to a retired PN officer) was to do a 'Hi/Lo' with the AW101 as the heavy/high-end and buy more Z-9 for the light/low-end. Leonardo also offered the AW159 (while highlighting engine commonality with the T129 of the PA and T625, which is a candidate for replacing Alouette IIIs in the PA and PN).
However, someone else (albeit from the industry) said the PN would rather move towards one ship-based platform, and it needs to be multi-mission. In this case, they asked for info about the NH-90 and MH-60. But, as you said, it seems both helicopters have a restriction, the simplest one being US parts (NH-90 uses a US engine).
That said, it turns out that the total cost (procurement, maintenance, etc) of the AW101, NH-90 and MH-60 is all quite close at around $100 m per helicopter. So, in the end, the PN could (as you said) just go for the AW101 and build around it. We might see an end of small ASW helicopters entirely; the PN could move to just AW101 for all naval and marine mission ops, while use the AW139 or T625 for utility and SAR.