America's "inaction" was a solid policy decision by an administration that didn't make many of them.
The U.S. didn't do anything to deal with the Houthis because the U.S. had no legal or diplomatic standing to protect ships that weren't flying U.S. flags and were not assets of U.S. companies.
“the U.S. had no legal or diplomatic standing to protect ships that weren’t flying U.S. flags and were not assets of U.S. companies.”
Are the Houthis going to sue us if we shoot down a missile that would otherwise destroy itself and an innocent commercial vessel mere seconds later?