Actually there are air passes available for foreign visitors to North America. For example the Star Alliance (airline partnership which includes Air Canada and United Airlines among many others) sells a North American air pass to foreigners in conjunction with a Star Alliance flight to North America. Information here:
Having said that, you'll likely find it much cheaper to buy point to point air tickets in advance of your trip, thus sacrificing flexibility but getting overall cheaper airfares. Check carriers such as Jet Blue, Virgin America and Southwest Airlines.
With only two weeks you need to really prioritize what is important to you. It is not really practical to try and visit all the places you listed unless you just want to say "I was there".
Coming from Oz you'll more than likely arrive in California, either San Francisco or Los Angeles. Assuming a full 14 days on the ground in the USA, then I'd consider the following:
Day 1,2,3: Los Angeles - 3 days, 2 nights. On the afternoon of day 3, transfer to Anaheim and overnight in Anaheim near Disneyland.
Day 4: Disneyland (Anaheim) - All day in Disneyland. Overnight again in Anaheim. In October, if you go midweek, Disneyland shouldn't be too crowded and with judicious planning you can get through it. Yes, there is California Adventure next door (separate park) and if you want to see that too you'll need two full days here meaning you'll need to cut back somewhere else.
Day 5: Fly in the morning from Long Beach Airport (LGB) to Las Vegas (LAS) on Jet Blue. Afternoon sightseeing in Las Vegas. Overnight in Vegas.
Day 6: All day sightseeing in Las Vegas. Overnight flight to New York City (JFK) on Jet Blue.
Day 7: Arrive NYC early morning, check into your NYC hotel.
Day 8, 9: SIghtseeing in NYC.
Day 10: Take bus (Megabus) or train (Amtrak) from NYC to Philadelphia. Overnight in Philadelphia.
Day 11: Sightseeing in Philadelphia.
Day 12: Fly to Chicago. Midway Airport (MDW) is closer to downtown and is served by Southwest Airlines. Chicago's O'Hare international airport (ORD) is further out of town but is connected to the city center by metro/subway.
Day 13, 14: Sightseeing in Chicago then begin the long slog home to Oz from Chicago (ORD).
Orlando and New Orleans are just too far out of the way compared to the other destinations and time constraints for this trip. I'd also save the Grand Canyon for another trip where you can perhaps dedicate a fortnight to exploring the national and state parks of the southwestern USA. The canyon has been there for eons and will wait for your return someday!