A caution, per se, doesn't require anyone to obtain a visa for the USA. However, the arrest which almost certainly preceded the caution does mean that you're meant to apply for a visa.
Since I posted that answer which you've linked to, someone has posted here on AB to say that they've entered the USA, with an undeclared conviction for the possession of class A drugs, without any problems. So it's likely that you'd get in without difficulty.
However, if you're the nervous type, you should be aware of this which appeared in The Independent on Saturday:
"The treatment meted out by US Immigration to so many visitors these days is shocking. Perfectly innocent people are effectively locked up for hours on end and humiliated in the name of security. . . . .In my few trips to the States I have been fortunate to pass through immigration without anything worse than having to stand in lengthy and slow-moving queues, but each time I have seen fellow passengers being hauled off, yelled at and questioned aggressively".
Chris