This is something that I thought I could read "between the lines" in several texts in the past (some of which might have been propaganda already in preparation for the war), but I never had the time to read up on it more thoroughly.
I was reminded of it recently because of the commemoration of WWI and how the US back in the time praised the bravery of the Serbs and their fight for freedom. Excuse my cynicism, but the first thought is what the US had to gain from either Serbia or Austria-Hungary or anything related to the conflict that was brewing, especially since the Habsburgs had no ambitions of becoming a colonial power and had interests only in their immediate neighborhood, so they probably were no opponent on the world stage outside of Europe.
I'd appreciate it if anybody could give me some insight on this.
Well the United States didn't enter the conflict because of the Serbian Crisis, they entered in 1917 because of money, Mexico, and submarines. The French and British owed the Americans a lot of money through war time loans and the American banks were terribly worried they wouldn't be able to pay it back if they lost, Germany owed the US a lot of money too but only 27 million compared to the Entente's 2 billion. The next reason for US intervention is the Zimmerman Telegram. In 1917 Germany sent Mexico a telegram (dubbed the Zimmerman Telegram) stating that if Mexico were to go to war with the US, Germany would financially support them and let them retake the land they lost to America in the war 69 years previous. The Telegram was, however, intercepted by the British and given to the United States which infuriated them and was the straw to break the camels back, but the biggest reason the US joined the war was that Germany had a strategy called Unrestricted Submarine Warfare. This strategy was that any ship in the Atlantic would be sunk without warning. This violated US neutrality when, in 1915, the Germans sunk two British passenger ships (picture the titanic) called the Lusitania and the Arabic. The Lusitania sinking resulted in the deaths of 128 American and the Arabic the deaths of 3. The outrage over these deaths and the later sinking of the French passenger ship the Sussex (no American lives were lost but this broke the previous 'Arabic Pledge' that the Germans would stop sinking Passenger ships) caused the Germans to give up Unrestricted Submarine Warfare with the 'Sussex Pledge' this pledge was later broken in 1917 when the Germans hoped that the Entente would break before the Americans would get involved in the conflict, the Entente instead held firm (except for Russia of course) and the Americans joined. As you can see none of these reasons involved Austria-Hungary (in fact the United States didn't even declare war on them until December of 1917, 6 months after their declaration against Germany) the United States didn't really mind the Austrians or the Serbian Conflict, their entrance into the conflict was all their own. They didn't stand to gain anything from the Serbian Conflict because their enemy wasn't Austria-Hungary, but Germany, in fact the only Entente Power fighting because of Serbia directly was Russia, and they surrendered a month before the Americans joined. You are right to assume the Austrians were no threat to American interests, because the Austrians weren't a threat to American interests and as such the Americans wished to remain neutral in the conflict. It was Germany, and the reasons stated above, that drew them in, not the Serbian Conflict or Austria being a threat.
Edit: Sources-The American Pageant-12th Edition, David Kennedy, Lizabeth Cohen, Thomas Bailey. A People's History of the United States - Howard Zinn