In the US current legislation does not establish limits nor compulsory heirs as in most countries in the rest of the world. Testator has the freedom to include in last will people or organizations without the constraints that other legislations impose to protect the family specially next of kin. Bearing in mind that your decisions might not interfere with spouse rights that can be contained in individual state laws.
Besides the estate distribution when the person dies without a will the court has to first of all probate that estate and secondly name an administrator for that estate. This is a long and expensive process. In most cases all the estate unknown by the court either because is abroad or just because it is difficult to certify is lost.
US intestate laws vary from one state to another. Most current succession legislations determined according to next in kin heirs and if there is no any, the estate passes to the state.