Refugees flood out of Ukraine into nearby countries. Humanitarian crisis and calls for international aid / assistance.
More COVID outbreaks due to refugees and bad living conditions.
Other eastern European nations will be interested in joining NATO or some kind of security pact so the same thing does not happen to them.
However, I have been lied to repeatedly by "news" organizations, so why not use the power of the internet to see how things really are? I did a search for live webcams based in Ukraine, and it looks to me like things there are actually quite normal. People are walking around the public squares, there are people skiing on the slopes.
Is there really anything more than political shenanigans to keep Ukraine out of NATO happening? I have reason to doubt it.
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If there is an actual invasion, I agree with alfanick, nothing much will change.