Quite la importacion del modulo de traduccion

App.js

 import React from 'react';
 import { StyleSheet, Text, View } from 'react-native';
 
-import { t } from './locales/index.js'
 
 export default function App() {
   return (
     <View style={styles.container}>
-      <Text>{t("Hola")}</Text>
+      <Text>"Hello"</Text>
       <StatusBar style="auto" />
     </View>
   );

locales/en.json

 {
-    "Hola": "Hello"
+    "Hola": "Hello",
+    "Hello": "Hola"
 }