“that the USA government cannot prove with certainty who is responsible for the alleged chemical attack?”
Could they possibly be a cache Sadam Hussains Iraqi WMD transferred to Syria before the shock and awe? If so whose protection were they ultimately under? Assad? Rebel forces? Russians? Therein lies the burden of proof. Better to be proof positive.
Very unlikely. From the images I’ve seen it doesn’t look like Sarin or VX. Those leave obvious signs in victims. This looks like possibly chlorine gas.
Chlorine is a poor choice for a weapon. It disperses too quickly and requires high concentrations to be weaponized which makes it unsuitable for use in munitions.
I haven’t dug much into this recent attack and looked at the evidence provided so far. The important things to look for are the claimed delivery system and the victim symptoms. Was this building shelled or hit with an air strike? Who has control of this area? Were the buildings multi story and how many areas were hit? What are the locals claiming? These details will go a long way to pointing you in the right direction.