You're calling async method unlimited time! You need to call it once via useEffect just when component rendered for first time:

import Parser from "rss-parser"; 
import React, { useEffect } from "react";

function Episode() {
  const parser = new Parser();
  const url1 = "https://anchor.fm/s/75abc654/podcast/rss";
  const [data, setData] = React.useState({});

  useEffect(() => {
    (async () => {
      let data = await parser.parseURL(url1);
      console.log(data);
      setData(data);
    })();
  }, []);

  return (
    <>
      {data.items?.map((item, index) => (
        <h1>{item.title}</h1>
      ))}
    </>
  );
}
export default function App() {
  return <Episode />;
}

Just replace your async function with a useEffect hook like this

useEffect(() => {
  async function fetchMyAPI() {
    let data = await parser.parseURL(url1);
    setData(data);
    // console.log(data.title)
    // data.items.forEach((item) => {
    // console.log(item.title)
    //console.log(item.pubDate.slice(5, 17))
    //console.log(item.enclosure.url)
    // console.log(item.itunes.image)
  }
  fetchMyAPI();
}, []);

This will be executed once every time when your component is loaded on screen

Also change the data.item.map to

{data.items?.map((item, index) => {
    return <h1>{item.title}</h1>;
 })}

Else it will throw error on first render