Lying to US authorities rarely goes well. The problem is that even being truthful can cause issues
Earlier this week, incoming Harvard freshman Ismail B. Ajjawi found himself blocked from entering the US. Ajjawi, a Palestinian resident of Lebanon, had landed in Boston before the start of classes. But The Harvard Crimson reported that after hours of questioning, US Customs and Border Protection agents revoked his visa. Ajjawi said a CBP agent searched his phone and laptop while asking questions about his friends’ social media activity. Then, she “started screaming at me,” Ajjawi said. “She said that she found people posting political points of view that oppose the US on my friend[s] list.”
It's really hard to say how consequential lying would be. CBP has broad authority to deny entry, and if a CBP officer investigates you and finds you omitted something it's possible they deny you entry. The most likely way you would get caught would be if CBP searches your phone on entry and finds undisclosed social media accounts.