they aren't masked behind national security, that IS the issue. China was asked to host data on US servers, so it garunteed they couldn't access the data, yet there's evidence Chinese employees were accessing the data. That's strike one. Now they have an app that can sway the public opinion of ages 8-30, by feeding them content that presents a certain perspective example: during the tiktok hearings in the past, on tiktok there were memes (probably boosted) that purposefully made lawmakers look stupid, even if they had reasonable questions. This swayed public opinion in itself. Also bonus, it gives access to some user data too. That's not to mention China doesn't allow a US based app like tiktok to exist in their version of the internet.