Sure it did. In the 1910s Congress' Commerce Clause powers wouldn't have encompassed purely intrastate commercial activity. The legal landscape was already changing, slowly, but in no way would a national law have been effective without a constitutional amendment. Heck, at that time the Supreme Court interpreted the ratified Prohibition Amendment not to apply to homemade liquor for personal consumption, despite the plain text of the amendment.[1] Compare that to Gonzales v. Raich (2005) where the Supreme Court permitted Congress to regulate, under Commerce Clause powers alone, homegrown marijuana for purely personal use.

Perhaps the line of reasoning you're alluding to is that, at the time, state and local prohibition laws were already so common that the Prohibition Amendment shouldn't have changed the effective legality of alcohol consumption for most Americans. But to maintain the status quo in perpetuity, locking in Temperance Movement reforms without defectors slowly eating them away, a national law was desirable.

[1] I'm still looking for the citation, but IIRC the reasoning was that the court wouldn't interpret the amendment to reach private, non-commercial activity unless it was explicit on that point; it wasn't just a cop-out textualist dance with the word "manufacture".

That is a far more well thought out argument than mine.

> But to maintain the status quo in perpetuity, locking in Temperance Movement reforms without defectors slowly eating them away, a national law was desirable.

But overall yes — this what what I was referring to. Even if I wasn’t clear on the state vs federal level, the overall argument that I’ve seen is that the proponents of prohibition wanted to increase the difficulty of rolling back prohibition. And if alcohol was banned through legislation, it would just take a single election (state or federal, depending on the law) to change things back.

> In retrospect, this strategy turned out to be pretty effective.

You think so? It lasted all of fourteen years and did very little to stop the flow of alcohol throughout the country. And I believe it's the only amendment to have been repealed.

If it were a legislative action, rather than an amendment, I suspect it would have been more effective in the long term since legislation is usually more thorough and detailed than constitutional amendments.

I think their referring to the 2/3 of the house and senate that voted for it and 3/4 of states ratified it.

Weather or not the law had the desired effect relative to hypothetical legislative action is an open debate but undoubtedly could be overturned with less votes.

> If alcohol was prohibited through legislative action,

Which it was, by the (post-Armistice, pre-18th-Amendment-ratification) “Wartime Prohibition Act”.