Congress believes it's a national security threat which is probably true but they haven't bothered explaining this to their constituents at all. Ideally they'd pass comprehensive privacy protection laws to setup standards that both domestic and foreign companies would be subject to. Then companies either adjust their behaviors and meet a certain level of transparency or they would be prosecuted under the law.
But no... We get this instead: a confusing and obviously targeted ultimatum with Congress telling everyone 'trust me bro this is the only way'.