Is it possible for the Native Americans to win at Tippecanoe? Under the Prophet, it's probably not likely, but if Tecumseh returned earlier (or never left), could they have defeated Harrison? What would be the ramifications for the United States? Would Tecumseh's confederacy gain more credibility among the other tribes? How would the British react?
Yes, it is possible militarily. Tecumseh was an excellent leader, and his goal would have been more limited - to defend Prophetstown, not to go on the offensive like Tenskwatawa. Attacking the American camp was Tenskwatawa's big mistake - Tecumseh would never have done that.
Defeating the Americans like that would have given Tecumseh huge credibility, and obviously keeping Prophetstown intact is a bonus too.
The Americans would probably blame Britain for their defeat - ironically, the Battle of Tippecanoe (probably battle of Prophetstown ITTL) might still spark the War of 1812.
MadMc wrote an excellent timeline on a similar subject. Check it out
here. He's very knowledgeable, and you can probably PM him any questions about the structure of the confederacy. Hope this helps!
Cheers,
Ganesha