React-Native: React could not be found within project or in these directories

I fixed it by replacing

import Foobar from "screens/foobar";

with

import Foobar from "./screens/foobar";

note the beginning ./ in the path

I was facing the same error when upgrading from v0.60.3 to v0.61.4.

I needed to change

import React, { Component } from 'React';

to

import React, { Component } from 'react';

Notice the lowercase 'r'.