An app used by young people to post silly videos definitely poses a severe national security risk[1][2].
[1]https://www.entrepreneur.com/article/340216
[2]https://www.wbur.org/hereandnow/2019/10/24/tiktok-most-popul...
[1]https://www.entrepreneur.com/article/340216
[2]https://www.wbur.org/hereandnow/2019/10/24/tiktok-most-popul...
It makes it easier when the people in that country who use the app are very easily impressionable children.
From the article that I suspect many did not read: "lawmakers questioned TikTok’s data-collection practices and whether the app adheres to censorship rules directed by the Chinese government that could limit what U.S. users see"
Metadata, GPS location, Camera/Photos and Videos can also leak information about people, specfically children/teens of high ranking officials.
"And the lawmakers said that TikTok could be a “potential target of foreign influence campaigns like those carried out during the 2016 election on U.S.-based social media platforms.”"
Is this fear different than what China says about USA tech like Google/Apple/Microsoft? Nope - same. They treat it differently and force companies to comply with their laws and rules.