What is the ruling on disobeying parents' command not to leave studies and return to the country to care for them, knowing that they are commanding me to stay and complete my studies, and they are in good health?

There is no harm in you remaining in the country of study as long as your stay does not cause your parents to be neglected. You are not obligated to return to your homeland to live with them. If they command you to stay to complete your studies, then you must obey them, as long as the studies are permissible and no harm results from them. However, one should be keen on residing in Muslim countries, as a Muslim's residence in disbelieving countries entails many risks to one's religion and morals.