Ethical according to whom?
Is there an agreed standard on what is ethical? As explained earlier in this thread, people often hold self-contradictory ethical views without realising it.
Historically a nation is a local population who defend an exclusive territory to provide for their current and future needs. A nation guarantees a distinct people a future place in the world, and independence, regardless of their wealth or material aspirations.
In modern America, Americans have no say over who can become American or indeed whether anyone else should have that right. Current politically-correct laws and globalist ethics / propaganda side with immigrants. Americans have no say over who can colonise their country, and consequently the future face of their nation, despite being the people who have historically invested in and defended their nation.
Is it unethical if a current majority within a country are opposed to being displaced, such as America's present Christian majority being replaced by Muslims in coming decades? Should larger populations in global terms have an assumed right to displace smaller populations who are presently a majority in their own countries? Should the wealthiest be able to acquire ever more property from those poorer than them? A nation defended remains the collective property of a population and guarantees freedom from slavery by a wealthy elite, or dispossession by outsiders.