This isn't really either that interesting or that telling a statistic.
First, most crimes people care about, in the sense of not wanting themselves or their loved ones to not become victims of, as murder, rape, robbery, fraud,... are and should be state crimes.
Second, because "improper entry" into the US by a non-citizen is a Federal crime, commissionable only by a non-citizen, there is a rather large bias at the Federal level due to this alone.
Third, many, many Federal crimes, including a lot that govern foreign trade and will thus more likely involve non-citizens, are crimes because Congress abdicated its responsibility and allowed the administrative state to create crimes, are the sort of things most of us on this board feel shouldn't be crimes at all, because of which fact the meaningfulness of aggregate Federal crime statistics as a gauge of actual wrongdoing is dubious.