While the U.S. has repeatedly referred to the crime against humanity launched against the Yemeni people by Saudi Arabia and the U.A.E. as KSA's war, it has provided both with large of amounts of technical assistance, intelligence, and equipment with which to fight it.
The United States has even engaged in direct combat from time to time, including a now infamous operation that left one Navy SEAL dead.
Now, however, the U.S. has stepped up its involvement to joint operations with Saudi and Emirati forces on the ground in Yemen. The operations have been reported on by the mainstream press but in scant articles that only hint around at the scope of American involvement. This has led many to suspect that the Americans are more heavily involved than what is being made public.