There are two likely outcomes in the event you decide to plead Not Guilty. You will either be acquitted or convicted. What it will be is difficult to say as it will almost certainly come down to whose evidence the court prefeers on the day.
As far as the "moral turpitude" bar to the US visa waiver programme goes, such offences are not clearly defined, though common assault does not seem to figure in most definitions. However, the US Embassy says that anyone who has been arrested (whether convicted or not) for any offence is not eligible for the waiver programme. (This is at odds with the waiver application form which suggests that only offences involving moral turpitude invoke the bar). You will have to enquire at the Embassy.



