Airlines do not "sell" nor do they arrange entry visas. They do, however, collect departure/entry/transit taxes etc. which is added to the ticket price. I think you are confusing the two.
It is fairly common knowledge that Australia requires visas for most foreign nationals including United States citizens. The visa is very easily obtained online and it is electronic. The airlines have access to that database and they can verify that you indeed have a visa to travel there. Relying on information from an airline reservation call center was a bad choice. They are not experts in immigration and visa matters. You also complained that the airline website transferred you to another website however the airlines do so as there are changes all the time and the most current information is maintained by IATA in their TIMATIC database. Most US airlines refer you to TIMATIC to inquire about visa and entry requirements.
Finally, you live in the greater Los Angeles area. Australia has a Consulate General in Los Angeles which you could have visited or called before traveling. They would most certainly have given you the correct information and guided you to the website to purchase your visas. Bottom line it is the travelers' responsibility to research and obtain the correct documents not the airlines'.
(And by the way...it's Qantas, not Quantas!)
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