The most up-to-date data for Brazil is maintained by IPEA, in the geobr dataset. We wrapped this dataset in GeoArtifacts.jl under the GeoBR submodule. You can use the package to download the data.
The data comes as geopackage files if I remember correctly. There are several packages in Julia to load the file. GeoArtifacts.jl itself will load the data for you, but you can use other lower-level packages as well. After the data is loaded, it should be easy to provide the information VegaLite.jl needs.