The brown longhorned beetle found in a shipping crate in Baltimore this week (see article here) serves as an excellent reminder that invasive forest pests are not a predictable bunch. Despite regulations on importing crates, the crate was made of non-compliant materials (presumably untreated wood, but the article doesn't actually specify). This is most likely why the beetle was found in the crate, alive and well, ready to attack the trees of Baltimore.
In the biggest picture, the reality is that despite a ban on certain imports since 2005 in the hopes of preventing the brown longhorned beetle from getting here, it is totally possible that the darn thing is already established at some port of entry in the US. Considering that this species attacks firs (most often thought of as the kind of tree used for Christmas trees), the repeated message from Don't Move Firewood that you can't judge firewood as safe to move solely based on the tree species rings especially true.