Given the recent holding of the US Supreme Court defining the age of consent for the general offense of statutory rape, the state statute is not a valid sentencing predicate, as the state statute is stricter, and a strict liability offense.
Government's post-briefing argument that the crime is a crime of violence under the instant provision of the sentencing guidelines refers to an earlier version of the guidelines with materially different language -- the older version cites crimes with a "substantial risk" of violence.
Contention that the sentence would be justified under another part of the guidelines is not properly before the court, as the question is simply whether the current sentence was correctly imposed.
http://www.ca5.uscourts.gov/opinions/pub/16/16-51009-CR0.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.