The Romanian phone site is at http://www/whitepages.rohttp://www/whitepages.roand one listing for SPIEGLER in the city of Bucuresti's phone book.
You will need to locate a name of a town for your ancestor in order to proceed with the research. I hope you are starting the research with what you know.If your father was born in US he should have SS-5Form (social security numbers). You can request that form which should provide his parents names and even maybe where they were born.
The Ellis Island website is listing 159 Spiegler that passed thru that port to America.You might want to start there.Maybe someone is an ancestor?