Fun fact about that embassy: it has on its grounds a monument dedicated to the brave American pilots who died on Bulgarian soil during WW2. What it neglects to mention is that those pilots died from Bulgarian anti-air defences ( including a heroic ramming in one case) because they were bombing targets, more often than not civilian ( as in cities, and the parts where people live), in Bulgaria.
If it were up to me the US ambassador would be expelled until that abomination honouring war criminals against Bulgarian civilians was taken down, but i see why nobody serious can afford to take action, the power disbalance is too big.