you'll get a residency no problem. As an IMG you'll find certain specialties extremely competitive. They're going to be competitive no matter what school you go to but make no mistakes - you will be more competitive in applying to a US program coming from a US allopathic school, how much so depends on lots of factors; scores, background, interview, US LOR's, etc. About a third of SDN attends this issue. No way to quantify. Pass your boards first shot, get the mean or above, wear a tie and smile, you'll have your pick of good academic residencies in primary care (Int Med, Surg, OG, Peds, FP/GP), and an outside chance at lesser known programs in more competitive things like ER, Gas, Rads. The currently "ultra-competitive" specilaites, like Derm, ENT, Plastics are going to be a long shot. Again, a long shot from anywhere. Competitiveness will vary hugely from year to year. Remember too that many specialities are post IM/GS fellowships, particularly the medicine ones.
Another point on the original post. Aussie doctors are different because in my experience they were generally nicer and more colleageal. Not all of them, but some of them. During my third year surgery block, I was in a AAA repair and cross clamped the aorta, and the guy coded and died. I felt just awful. The surgeon said afterward "get your gear mate". He knew it was a weird experience for me. He took me out, bought me a nice steak dinner and got me drunk. Totally unlikely and perhaps even irresponsible by US standards. For me, it was a profound experience in learning and the fraternity/sorority of physicianhood.