Because one of her sons turned his back on her, now my mother wants to draw up a Will in which she will give the remainder of her real estate that is legally hers to her other son.

All the real property is in another country that is very friendly to the USA (not sure if that will make any difference). We know the land is recorded in her name, but we don't know the exact description of the property without visiting the recorder's office in that country. We do know the name of the city where the land is located. Can my mother draw up her Will here in the states and in it she will only refer to her land in general terms, something like " all the land I own in X city", or any kind of phrase that can be very inclusive and understood to mean "All" the land owned by her in that city ? And will this document stand in that country's legal system ? Thank you.

I doubt an estate attorney would let her be so vague in her wording about the real estate description. If it is in a different country, that needs to be addressed in quite specific terms and descriptions. She needs to have her new will drawn up by an estate attorney to have the will stand up in another country so the one son could properly inherit the land.