Our embassy is sovereign territory too and short of pulling every single American out, our Marines maybe their only defense.
LOL. Our Embassy exists in Khartoum with the approval of the Sudanese government. We don't force countries to have an American Embassy. It is reciprocal when you decide to have diplomatic relations with another country.
If we pull out completely, it is up to the host government to respect our property. Usually, if we terminate relations with a country, we designate another country to represent our interests or in certain cases we will locate US diplomats in another courtry's embassy and set up a US interest section.