Q: Why are US naval resources being used for aggressive purposes (e.g., bombing Syria and threatening North Korea) but not for defending US commerce on the high seas?
A: Because the US military is being used to achieve global governance for the benefit of Western banks and corporations. We The People get to pay for it, while the banks and corporations hoard their cash, much of it offshore.
It's "war is a racket" all over again:
"War is a racket. It always has been. It is possibly the oldest, easily the most profitable, surely the most vicious. It is the only one international in scope. It is the only one in which the profits are reckoned in dollars and the losses in lives."
MG Smedley Butler