I live in Australia (or some place that is not the UK or the USA).
I wonder if the same percentage of QUALITY scripts get published in any place, but that in the big places, like the UK and the USA, there are many more scripts published that are of dubious quality, making it seem as though it's "easier" to get published if you live in the States.
Is where I live going to have a positive/negative effect on getting a novel published?
No, your location will not have an effect on getting published. Publishers are in this business to make money and as much of it as possible. If you have a good manuscript they'll buy it whether you live in New York City, the middle of Australia or in an underground tunnel with dwarves.
In the old times, location was key because you needed to be near the publishing houses or wait forever for mail. But with the internet, you can submit manuscripts instantly and have a response in a reasonable amount of time. Contracts can be emailed and either scanner or faxed back, further cutting down on the timeTweet