Todd Spangler NY Digital EditorWithin two months, TikTok’s U.S. business likely will be under the wing of a new owner — after Donald Trump’s move to force China’s ByteDance to divest the popular video app over what he says are national-security concerns.Amid that backdrop of uncertainty, TikTok is carrying on in business-as-usual fashion: Starting this week in the U.S., it’s unleashing its biggest ad campaign to date, aiming to lure even more American users to the platform.