Nothing will change except you stand at TIA "foreigners" line and you pay fee to stay in Nepal, I think $30 for 3 months but not sure.

 You don't have to give up Nepali citizenship and passport (but by law, yes you do). Only if somebody tells the Nepali authorities that you are an American citizen, and you still hold Nepali passport then you will face consequences. This is very rare.

My suggestion is transfer you properties to your love one just to be in safe side. Don’t tell people you don’t know or don’t trust that you are an American citizen.