One video allegedly shows the FGM-148 Javelin missile destroying what is believed to be a Daesh truck.
Washington has long denied that it provides arms to the PYD -- in an attempt to appease its NATO ally, Turkey, regarding the PYD's connection to the terrorist PKK.
The PKK is a designated terror group also by the U.S. and EU.
"We are providing equipment that is tailor specified to the next objective ahead to the Syria Arab Coalition (SAC), who is working with Syria Democratic Forces to move ahead just as they are doing in Shadadi right now," Davis added.
The SAC was unknown to most observers until last October when the U.S. announced an airdrop of 50 tons of ammunition to the group-characterizing it as 5,000 rebel troops fighting Daesh in the northeastern Hasakah province that has been under PYD control.
A spokesman for the U.S.-led coalition told reporters at the time that the SAC is a partner with the Syrian Democratic Force, an alliance of several rebel groups led by the PYD.
The airdrop also gave rise to concerns that U.S. weapons and ammunition provided to the SAC were transferred to the PYD.
Capt.Davis reiterated the long stated Pentagon policy of arming anti-Daesh forces saying that the arms and ammunition that the U.S. provided to the SAC were provided "on a performance based system".
"We assess what their needs are for the next objective, provide them the things they need to conduct that objective then assess how they did in that objective before we take the next steps for the next objective," he added.
Davis also noted that the Pentagon has not seen any evidence that the group has used any of the supplies for any other purpose other than fighting Daesh.
At times, however, pictures surface on social media showing YPG militants with U.S.-made arms.