calling externally componentDidMount() in react

I have a requirement in which once page gets loaded my dropdownlist should be populated. for that I put that code in componentDidMount().

  componentDidMount() {
    axios.get(`http://localhost:8080/country_code`).then((res) => {
      const countryData = res.data;
      this.setState({ countryData });
      alert(countryData);
    });
  }

I have one user input field in which person enter the value and save it into database. I want once user save that value into DB, my dropdown should get refresh and that value should be visible in the dropdown. so how can I externally call componentDidMount()? is there any better way to handle the same?
As of now list is getting refreshed only when user resfresh the page.