People are always in shock when they are denied entry and turned away at the U.S. border due to an old criminal record. They are usually in shock because they never thought it would get in the way, or they traveled in the past and were never denied entry.
The Americans do random criminal checks which have become more common, so even if you have traveled safely in the past, there is a high likelihood that you will be stopped at the U.S. border and denied entry if you have a criminal record or even if you have been charged with a criminal offence and the charges were later dismissed, withdrawn, stayed or discharged.
Once you have been denied entry to the U.S., you will need a U.S. Entry Waiver (I-192 or I-194) to return. The process of obtaining this application can be lengthy and complicated.
If you have never been denied entry to the U.S., it’s important to obtain a Pardon / Record Suspension or File Destruction so that your criminal record will be removed from record and cannot be seen by the Americans.