I am a US citizen (born in Europe) and are separated from my husband. If I decide to move back to Europe and change back my citizenship, will I loose my IRA savings her in the US? I am not 59 1/2 yet, and don't really want to take the money with me.

You can manage the IRA in the U.S. from Europe. Taxes will be due when you withdraw the money and probably will e taxed at 30% (unless reduced by tax treaty with your new country of citizenship).