Sure. It's completely possible to build a house in the US. But it's a big place. The rules vary by state (50), by county (Ohio alone has 87 counties), and mu

Sure. It's completely possible to build a house in the US. But it's a big place. The rules vary by state (50), by county (Ohio alone has 87 counties), and municipality (if in a city) or township (if rural), and/or other AHJ. There are thousands of combinations of rules so it's hard to generalize beyond "Yes, it's possible." Some areas have very strict zoning, building codes, and inspections. These can be challenging to build in, with oversight over many details, but it can be done and people do accomplish building homes all the time in these conditions. Meanwhile, some other areas have no zoning at all and only the most rudimentary of building codes (rudimentary like "There must be a working sewer connection or septic system" and approximately no other requirements). As a practical matter, in these places a person who owns some land can build what they want and nobody is empowered to tell them not to. And, of course: There's a myriad of in-between variations.