Hi!I'm 21 years old and I'm french! I came here with a visa for 1 year as a nanny.my year is almost over and I have to go back to france. But I'm getting married at the end of January! And even with the marriage it s seems hard for me to come back here! I need help with how to be a citizen, what I need to do, how long does it take... can I even have the dual citizenship? Please I need help.. I really want to be able to come back here and live with my husband! thank you

From the US State Dept: "The United States does not recognize dual citizenship; however, it does not forbid it. Despite the fact that we allow citizens to hold other nationalities, the U.S. government's view is those people continue to be U.S. citizens, period."

And check the USCIS website:
http://uscis.gov/graphics/howdoi/lpreligibility.htm

Get married before you leave the country and then petition to stay.

Perrine here is the good news.. as long as you entered the US legally your husband can petition for your visa while you are back in france and you just have to wait for everything to go through. I am actually going through the same sitauation except I am not going to be able to marry my fiancé before she has to go back to taiwan.. So I have to do the fiancé petition to get her back.. The key to everything is that "originally you entered the country legally" That is the most important thing to the US.. technically you could hide out for a while (I don't suggest it) and they will hold nothing against you because you came in legally. But if you enter the country illegally.. they will not help you