This is honestly sort of impossible to answer because you never know what happens in the alternative reality where Kerry won - maybe it started a butterfly of events that ultimately lead to the US being a significantly better/worse place than it is now, maybe Trump would never have gotten into politics and we wouldn't be in the situation we are in now, ect.
If Kerry won in 2004, Obama probably never would have been president. In fact, it’s possible Obama runs in 2012 and loses the general election to either an incumbent president McCain or if Kerry was re elected in 2008, he loses to another Republican.