Making multiple async call in a row from anonymous async function

Question

   const loadJSON = () => Promise(
      async () => {
         const req = await fetch(`data.json`);
         return req.json();
      }
   );

   const loadData = (city) => Promise.all(
      city.map(async (f) => {
         const req = await fetch(`${f}/geo.json`);
         return req.json();
      })
   );

   (async () => {

      const loadedJSON = await loadJSON();
      console.log(loadedJSON);
      const loadedData = loadedJSON.map(f => f.loc);
      console.log(loadedData);

   })();

data.json just contain an array of cities (like London, Barcelona etc). With the second function I want to get the cities locations (cities location are at the city_name/geo.json file)

If I only use the loadJSON and the appropriate parts of the anonymous async function, I am getting the following error message:

Uncaught (in promise) TypeError: undefined is not a promise
    at Promise (<anonymous>)
    at loadJSON

What is the problem with my code?