Somebody recently mentioned, here on AB, that their partner had been refused a visa because of 2 convictions for driving with no insurance, so it seems quite likely that anyone with a driving conviction which led to a prison sentence would be refused.
The US authorities don't recognize the Rehabilitation of Offenders Act so, as far as they're concerned, your offence will never be spent. (Unless you were aged under 18 at the time of conviction, your offence won't be 'spent' in the UK for another 4 years).
As has been frequently stated, the US authorities have no direct access to UK criminal records so you could probably enter the US (illegally) by simply 'forgetting' about your conviction on the Visa Waiver form.
Chris