"Deep history" of the US-Serbia relationships

The next US President congratulates Serbia on Statehood Day, emphasizing the deep history of relations between the countries... What is the real depth of this connection?
Milica Rakic would have turned 25 this year. But she died at the age of three in 1999 in a bombing raid during NATO's Operation. The war took lives of 1,700 civilians, including 400 children. In the former Yugoslavia, many cancers are caused by the use of radioactive depleted uranium in munitions.
Was the US President talking about this connection?

A video about Milica and other children of Serbia was also released in Serbian and Russian.

Видео "Deep history" of the US-Serbia relationships канала Русский дом