When looking at the Australian Ford sites keep in mind that there is a strong Asian influence in those vehicles, a lot has to do simply with proximity. However, I don't believe that their Ranger and the Nissan are the same, while there are and have been some links between Ford and Nissan, I don't see that here, I would be quicker to believe a Mazda link rather than Nissan.
If you look close at the radio and dash, the Radio in the Titan is similar only in layout, the overall dash shape and function layout is different. The Dash of the Frontier is not at all like the Ranger.
The Falcon series is sort of their answer to our Mustang, although in a 4 door sedan. I'm not sure how close the newer ones are to our current Mustang chassis, but I would guess there's still some similarities. The Falcon is however an Autralian built and designed model and not a mere rebadge or reskin of our Fox body cars.
The Ute body style has always been common there as well. There are many Ute versions of many different models there, not just the Falcon.
Keep in mind that down under they also still have a Courier model too, that probably more or less fills the slot that our Ranger does here, therefore the Ranger is offered as a slightly larger vehicle that may be just a bit less truck like. The Courier looks to be marketed to the commercial market and the Ranger looks to be more geared for the general public.
Check out this for comparison to the Ranger:
Here's a link to the main Ford site for Australia: