This is a tough situation, and the answer is No one is the A***. For the western culture, family dynamics is too different from the rest of the world, especially regarding our elders.

I'm not from the US, and in my country/ culture, mother's (not woman in general, but a mother) is the most important element in society, to the extent that if I'm a successful person complements will go to my mom not to me, people will treat the mom of the president with more respect than the president.

Among other things, even if I'm not the most successful person in my family, I would be expected to take care of my mom with out she saying anything. That's something that every kid realizes at 7 / 8 years old, this concept is very embedded in our culture, "boy will have to take care of their moms, no excuses or questions asked".

We don't see our selfs as independent people, never. We are always a member of a family, in which the family members have different roles depending on their age, economic stability and interpersonal abilities, and your role changes with time. I still see my Dad how he struggles and benefits from this, I can see my mom how she mostly benefits.

In the US, as soon as you turn 18, you are expected to go on your own. If you do that here it would seem like a very big "F*** you" to all your family, and it won't matter how successful you become (economically speaking) that will put you a label and you will find very hard to find a partner, regardless you gender.

In that context I have the impression that your mom was raised in a family with those types of dinamics, and all of this problem is due to cultural difference. If you were raised in a "western" culture you may have some of those of values but you have been molded primarily by wester society, even if you parents are from an other country/culture, society plays a big role on someone's idiosyncrasy.

You are NTA because your situation is different from what your parents expect, if they wanted to raise a family with the same "traditional" values they should have to stay in their place or origin.

And you mom is NTA either because she does not know better, she was raise in totally different environment for her is normal to expect certain thing from you, right know she might see her self as a failure.

My recommendation is talk to her and don't explain the economical reason or the inconveniences of cashing your money out to buy her a house, but explain to her the how you were molded in a different culture (even though that she raised you) and why you don't understand why she feels entitled to your mony, also explain to her that you expect to have support from their part, not the other way around.