No, not all convictions will make you inadmissible to the United States. While most criminal convictions will provide sufficient grounds for a border official to deny you entry, the US border officials are given significant flexibility in determining whether or not an individual can be admitted into the United States.
The principle criteria for whether a not an offence will render you inadmissible to the United States is if it is deemed an offence of “moral turpitude”. The term “moral turpitude” can apply to a wide variety of offences, but the most common elements of moral turpitude offences are:
- Larceny, and
- Intent to harm persons or things
In addition, while they might not fit clearly into any of these elements of moral turpitude, drug offences are definitely considered by the United States to be offences of moral turpitude, and will almost certainly result in a denial of entry.
Whether or not your offence(s) contained these elements to a significant degree will depend on the circumstances of the offences themselves, and so it is generally best to be honest and co-operative with the border officials if they ask you for the details regarding your specific offences. Some offences are generally not thought to be of moral turpitude, such as many driving offences. For example, U.S. Customs and Border Protection has been consistent in permitting an individual entry into the United States with a single impaired charge or DUI on their record. In cases where there is more than one of these offences, the border officials do reserve the right to deny you entry.
Crimes that make you inadmissible to Canada will not necessarily make you inadmissible to the United States. For example, the United States does not normally bar people with drinking and driving convictions except in rare circumstances.
If you do have a conviction that makes you inadmissible, you should apply for a US Entry Waiver.