Does a person's return to his country and his refusal to build his mother's land count as cutting off sustenance, and does his mother's anger because of that necessitate God's anger, knowing that building the land will negatively affect his ability to provide for his family?

The obligatory expenditure for the wife and children takes precedence over the expenditure for the parents. If the mother is not in need, she does not have the right to her son's money without his consent, nor does she have the right to take from his money what would harm him or give it to others. Therefore, there is no blame upon you for refraining from building the house your mother desires, nor for returning to your country, and you are not considered disobedient by doing so. You must continuously honor your mother and strive to please her, and you can gently apologize to her without an outright refusal, using tact, subtle hints, and allusive language.