@Dropbear, given the cost disparities between Aus & the US, I understand the impetus to either ‘go big’ or stay home! And, depending on your overall goals, the differences at undergraduate level may not be that important. The courses for a physics major at UMelbourne are pretty much the same as at an American uni. The main differences would be:
=> at some US unis you could have more ‘breadth’ requirements,
=> at larger unis you would have other course options within the physics major
=> at most unis (and many colleges) there would be opportunities to do research at the undergrad level. The grad-school bound physics undergrads that I know (even at smallish LACs) will have done research (and frequently have been co-authors on a couple of publications) during the summer breaks and/or during term.
As for other options…
The [url=<a href=“http://www.shanghairanking.com/SubjectPhysics2015.html%5DShanghai%5B/url”>http://www.shanghairanking.com/SubjectPhysics2015.html]Shanghai[/url] rankings puts Melbourne in the 100-150 group, and there are dozens of US universities in the 0-100 groupings.
QS world currently ranks Melbourne as #45 for physics globally. Although I take all rankings with a lump of salt, and subject-specific ones tend to relate more to grad than undergrad, some other US unis that they rank ahead of Melbourne include: UPenn (#44), UTexas (Austin) (#38), UMaryland (CP) (#34), UMichigan (#32), UIllinois at Urbana-Champaign (#30), UCLA (#17), UCSB (#15), and UChicago (#12).
Note that UCs are one application, so you can do B, LA, & SB at the same time, and I would add Irvine as well. QS doesn’t rate it particularly highly (100-150), but Shanghai does (45), and I know a professor there who is doing great stuff with his undergrads.
Penn & Chicago are private, not state, unis and have admissions rates of 10 & 8% respectively. The others all have strikingly higher admissions rates, and you could add any of them to your list.
The UCs are the most expensive for out of state/international (and you won’t have state residency for California for at least a year after arriving), but none of them are as inexpensive as Melbourne. Btw, some are more expensive for international students than out of state, so if you have your US address before applying there can be some savings there. If finances are an issue and you test well there are some great merit scholarships, though typically at somewhat lower ranked places.
Finally, the College Data Common Data Set (collegedata.com) will give you a lot of info on admissions, including what the uni says is most important to them and the breakdown of stats on admitted students. For example, for CalTech, the ACT score range for the middle 50% of admitted students was 34-35; how rigorous your secondary school course load was way more important than whether you did volunteer work; the admissions rate for males was 6% and for females 16% (and 3x as many males as females applied); and from an initial wait list of 615 they took 47 people last year.
Oh- and I suppose that you have worked out the Early Decision / Early Action element? With ED you say that you promise to come if you get an offer, and your prize is that you know in December if you are in, deferred to regular admissions or out. You can only apply to one uni ED. With EA the uni tells you early, but you don’t have to commit until all your decisions are in- usually works best if you are somebody they are likely to want. Single choice early action (SCEA), which Princeton uses, is also non-binding but you can only apply EA to one private uni (state unis are fine).