[Edit] To be clear, there is nothing unique about the New Jersey statute that was used as a sentencing enhancement. As many states do, Arkansas has a similar statute - A.C.A. § 5-41-104 - so the sentencing enhancement could have been applied with Arkansas as the venue. The E. Arkansas US Attorney's Office exercised prosecutorial discretion by not seeking indictment. The New Jersey USAO decided they wanted to prosecute and thought they could make a colorable claim on the issue of venue.
The prosecution tells us much more about the New Jersey USAO than it does about the overall desire of the US Government to prosecute this particular act.
The more likely explanation, as others have pointed out, is simply that the U.S. Attorney for the District of New Jersey is the one who wanted to bring the case.