NATO is a rootkit, a foothold for lateral movement in a literal sense, for the US in Europe. Is is not "critical" for anyone, in some theoretical sense, but it has proven very effective over the better part of a century to keep European military in check and guaranteed not to form any other alliances than with the US.

The EU itself was viewed critically from Washington until it could be proven that it had no intention of becoming a military alliance. So while it could be true that the US does not need NATO in a strict sense, the idea that it has not been net beneficial to the US is absurd. No Danish soldiers would have died in middle eastern wars if it wasn't for NATO.