回複：綠卡,我的朋友(18歲)媽媽是美國公民,今年5月他媽媽幫他申

if 他已經拿到了綠卡 (unconditioned GC), which means I-485 approved. The sponsor can not cancel the GC.
But if the I-485 is still pending or the GC he has is with condition, the withdraw by the sponsor can kill his I-485/conditional GC.