There are only certain crimes which the U.S. will deny you entry for if you have a criminal record, most of which are violent or drug related. If it's a simple assault charge or uttering threats there shouldn't be any hassel provided you tell them the truth about any questions they ask. Don't try to lie because they can look it up in the computer and will know you're lying (I think that's part of how they can tell you are who you say you are). Keep in mind though, that border guards can deny anyone for any reason, you don't have to have a criminal record, so it's best to keep your opinions on their line of questioning to yourself. Just be calm, be polite, answer their questions (but don't give them any extra info, just answer their question as simply as possible and leave it at that. If they want more info they'll ask)
I can't stress enough about telling them the truth if they ask about a criminal record or being arrested or fingerprinted. They WILL know and if you lie they can confiscate your vehicle, belongings and even have you charged with fraud.