You're talking about people already in the US (citizens/residents). If you're trying to get a US visa from your country and you have a DUI on your record, it makes it much more difficult to get approved.

FYI, a US citizen with a DUI will likely get denied entry into Canada -- you usually need to be deemed "rehabilitated" or be granted a temporary stay visa before allowed in.

https://help.cbp.gov/app/answers/detail/a_id/402/~/entering-...