Well, this is an ENORMOUS question!
I would say that Ives occupies a very UNIQUE place in American musical culture -- because some regard him as one of the most important (perhaps THE most important) "classical composer" that America has ever produced -- while others regard him as something of a crank, an amateur who specialized in outrageous effects.
I suppose it's obvious that I align with the former rather than the latter.
If you haven't seen it, you might want to explore the site that I built in Ives' honor. It's quite old now; I haven't touched it in nearly 20 years. But most of the information is still relevant. https://www.musicweb-international.com/ives/
Exploring the site will give you a better sense of why I hold Ives' music in such high regard.