Is the phrase "la ilah" (no god)—whether uttered intentionally or unintentionally—considered an act of disbelief that expels its speaker from Islam, and what are the consequences of that?

One who repents from sin is like one who has no sin. If you have repented and regretted what you did, then your acts of worship are valid, and you must not repeat such an abomination. If this statement was uttered by a person of unsound mind, then there is no sin upon him. However, if he knows what he is saying, then denying the existence of Allah or His knowledge of His servants is disbelief (kufr), and the intention to disbelieve is not a prerequisite for apostasy. As long as you have repented, all that is required of you is sincere repentance.