No. Destruction of US government property and the corresponding lack of protection by the Serbian government makes it an act of war, no matter if no American was harmed. Personally I understand why the Serbs are pissed off. I live in a state that Mexico would love to have back, so I don’t think it’s OK for us to recognize Kosovo as independent.
Serbia is probably going to be going to war with Kosovo, and probably no later than April or May. The declaration of independence by Kosovo was an act of war against Serbia. Our recognition of the independent status of Serbia is just as much an act of war against Serbia as the Serbian Government's failure to provide protection for our embassy.
The US Embassy is sovereign US territory and it is up the United States to provide protection for it. The embassy was abandoned before this protest. The US knew it was going to happen and instead of standing and fighting, the US abandoned ship and essentially invited the protesters to burn the place to the ground.