National Prohibition was extremely ineffective. Prohibition did not stop people from drinking. Instead, it simply worked to make drinking seem glamorous and to put more money in the pockets of gangsters like Al Capone.
Prohibition was very poorly enforced. There were not enough agents and they were underpaid. To make things worse, most people simply did not think that drinking was really wrong so they did not stop doing it. This was helped along by the fact that drinking wasn't illegal. It was illegal to manufacture, sell, or transport alcohol, but not to drink it. So drinking became a way of doing something daring without doing anything that was actually illegal.
Prohibition, then, changed culture by making drinking seem like a more glamorous thing that was exciting for middle class people. This was a change from the days when it was seen as something that immigrants did in seedy saloons. Prohibition also changed society by allowing for the rise of organized crime. Al Capone made $60 million in 1927 from his bootlegging and other illegal activities. This would never have been possible without Prohibition.
Prohibition, then, was a huge failure that did not affect American society in the ways it was meant to.