For Canada you have to complete an ETA form, (introduced a couple of years ago and is similar to the USA ESTA form) and that asks “have you ever committed, been arrested for, been charged with or convicted of any criminal offence in any country/territory?”
The Rehabilitation of Offenders act does not apply, you have to declare any such offence EVER. A drink drive conviction makes you ineligible to enter Canada for a period of 10 years, but I understand they MAY consider exceptional circumstances. For this though you would need a VISA, not for you to enter under the ETA procedure.
For entry to the USA, the ESTA form asks a question with wording similar to: (note I cannot access the exact wording without starting to complete the form). “ have you ever been arrested for any offence involving serious injury to another person, serious damage To property (that would not include your own car) or significant loss to your Government?”
esta.cbp.dhs.gov
You should only use the link to the official US Embassy website. There are a number of other sites (including tour operator ones) which have the old form on it and the wording on them is NOT correct. (And they usually charge an inflated fee)
For drink drive purposes that would mean an accident with serious injury to other passengers in yours or another car (or pedestrian) or damaging several cars (or one very expensive one!)
So if you can answer “NO” to that question you are eligible to complete the ESTA registration rather than go down the Visa route. This would not apply for multiple drink drive (or other drunkenness offences) as they view several instances as a problem under their Mental Health restrictions.
If you do need to apply for a visa for work, or because you are ineligible for ESTA because of having a stamp in your passport to Iraq or other similar countries, then the question on the Visa form is like the old question that they used to ask on the ESTA form: “Have you ever been arrested for any criminal offense?” and if you have a drink drive conviction in the past 5 years they will probably require you to have a medical (cost about £320) before they will consider granting you entry.
simple isn’t it? !!!!!!!!!!!