I don’t remember the exact details, bit I think the Syria situation was more like:

the US knew it was Russia, they called up and down the chain of command for 4 hours while restraining their defense and avoiding significant attack. Every person they spoke with denied it was Russian. The US then let everyone know that they would attack if the attackers did not retreat. Another hour went by, and they destroyed all enemies.

Edit: https://en.m.wikipedia.org/wiki/Battle_of_Khasham https://taskandpurpose.com/news/russian-mercenaries-syria-firefight/