You seem to be under the assumption that there's some kind of linear path that cultures evolve along with fixed stages representing levels of development. That's not really how it works. People create technologies to respond to perceived social and environmental needs, and those needs depend on the context. You can't really take two cultures and describe them as existing at the same "level."

Terms like Paleolithic, Neolithic, Bronze Age, etc. are chronological markers used to describe particular periods of time in particular parts of the world. They're not levels of cultural development. Archaeologists will define characteristics for each of these chronological periods (such as the presence of agriculture during the Neolithic, or bronze tools during the Bronze Age), but this is isn't intended to be used as a description of the level of cultural advancement. It's more like a shorthand that helps us put things in chronological sequence, so if we find bronze tools but not iron at a site we know it belongs to the Bronze Age.

Because of this, chronological periods designed to describe European chronology are not used in the Americas. Instead we use different chronological indicators, like Paleoindian, Archaic, Initial Period, Formative, Classic, and Postclassic for Mesoamerica. If you were to attempt to fit native American cultures into the European chronologies using their indicators, you'd find it doesn't fit. (A bit like trying to squeeze a square peg into a round hole.) For example, Mesoamerican cultures during the Classic Period had agriculture but no Metallurgy, similar to the European Neolithic. But they also had large metropolitan cities, paved roads, hierarchical states, and expansive empires, which in Europe and western Asia are more characteristic of the Bronze or Iron Age cultures. The Norte Chico civilization of the coast of Peru had large settlements (almost small cities), mounded architecture, and some kind of emerging government, which in some parts of the world is characteristic of the Late Neolithic/Early Bronze Age. However, they had no ceramics and very little agriculture, so it doesn't really fit neatly into that category.

So ultimately, a culture's "level" of development is unique to each culture. Each group of people follows their own path and they don't all lead in the same direction.

As for your second question, obsidian was widely used across the Americas and was not limited to Mesoamerica and South America.