WASHINGTON (Reuters) -TikTok's chief executive faced tough questions on Thursday from lawmakers who are convinced the Chinese-owned short video app should be barred for being a potential national security threat to the United States. CEO Shou Zi Chew's testimony before Congress capped a week of actions by the Chinese company aimed at convincing Americans and their lawmakers that the app creates economic value and supports free speech. TikTok, which has more than 150 million Americans users, has faced sharp accusations that its U.S. user data would be shared with the Chinese governm...