Has advising Muslims become an individual obligation on every Muslim? Is inviting non-Muslims more prioritized than advising Muslims now? Is advising Muslims in Islamic countries more prioritized than advising Muslims in other countries?

The fundamental principle is that advising Muslims, enjoining good, and forbidding evil are a collective obligation (fard kifaya). It becomes an individual obligation (fard ayn) when there is no one else to fulfill it, and this applies equally to Muslims in Islamic lands and in lands of disbelief. As for inviting non-Muslims to Islam (da'wah), it is an obligation, and there is no impossibility in combining it with inviting and advising Muslims. If both obligations conflict, then one should strive to prioritize the greater of the two benefits. It may be that inviting a disbeliever takes precedence due to the grave danger of shirk (polytheism). If their acceptance of Islam is hoped for, then it is more deserving of priority. However, if their acceptance is not hoped for, then advising a Muslim, enjoining good upon them, and forbidding evil from them takes precedence.