CSV, KML, GPX and Shapefile all become datasets with fields, stats and a default layer.
A CSV with latitude/longitude columns becomes a point dataset; population is detected as a measure and drives the size scale.
Placemarks from a KML file, drawn as flag marks with the placemark name as label.
A GPX track as a line and a zipped Shapefile as polygons. Both are parsed server-side, fields inferred, geometries made valid.