You have to declare this on your application form and they will tell you whether you will be let in. Without pre-approval, no one can fly to the US (well no foreigners):
Crimes involving moral turpitude – Such offenses generally involve conduct which is inherently base, vile, or depraved and contrary to the accepted rules of morality and the duties owed to persons or society in general. There are factors, such as the age of the offender or the date of the offense, that may affect whether an offense will be considered a crime involving moral turpitude for purposes of the Immigration and Nationality Act.
For further information refer to § 212(a)(2) of the Immigration and Nationality Act, 8 U.S.C. § 1182(a)(2), § 101(a)(43) of the Immigration and Nationality Act, 8 U.S.C. § 1101(a)(43) and corresponding regulations in the Code of Federal Regulations.