is there an application, with which I can convert 3D models of long straight roads to realistic and accurate .usd objects which are aligning/adapting on the real curvature of the Earth (surface), while being geo referenced to the Earth’s center as origin?
I don’t believe there is, currently. However, the AECO Interest Group at AOUSD is actively engaged in these kinds of workflows and representation, with one focus being representation of geospatial coordinate systems in USD. The link I included contains information on joining as a free contributing member so that you can participate in the discussion with other practitioners.