import React from 'react';
import styled from 'styled-components';
import './App.css';
import { Header } from '../src/Components/Header';
import { GlobalStyle } from '../src/Components/GlobalStyle';
import { Menu } from '../src/Components/Header/Menu';

const AppContainer = styled.div`
    display: grid;
`;

function App() {
   return (
            <AppContainer className="App">
                    <GlobalStyle/>
                    <Header/>
                    <Menu/>
            </AppContainer>
  );
}

export default App;

Eu recebo o seguinte erro ao fazer essa conversão:

Error: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: object. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports.

Check the render method of App.