The proportion of "homegrown" to "...imported?" PhDs varies depending on your discipline, but at the science end of things (I'm in computer science, but know plenty of mathematicians and also majored in chemistry as an undergraduate) it's quite international. Apart from pathological cases (known "bad" universities, or otherwise extremely dubious universities), where you got your PhD is not particularly important. As Jeromy says in another answer, international experience is definitely viewed favourably though. My having done my doctorate overseas has definitely been a boon.
The real criteria are performance based; publications, teaching (especially awards or other recognition) and ability to bring in the grant money! (That last one in quite important, for better or worse). As a recent Doctorate, you'll mainly need to show that you can conduct quality research.
Just for some completely non-statistically-significant stats, my Australian undergrad. chemistry department had about 50% overseas PhDs, my CS department had more like 90% overseas PhDs and my maths department had about 50% too. At my current (Australian) department (CS), it's probably about 70-80% overseas PhDs (though that's a guesstimate at the moment), including me.
Of course the caveat is, again, this will change from department to department and university to university. Some like to only hire their own graduates, others will never hire their own graduates. Your best course is really to contact the academics offering the jobs, establish a bit of an informal relationship and find out what each position is looking for.