A good politician never lets a catastrophe go to waste. U.S. may not have purposely caused the invasion of Ukraine, but it's certainly a useful tool to rake in those NATO holdouts.
The only one to blame for the invasion, or the fact that new countries are joining NATO is Putin, and his political colleagues.
Making it seem as if Finland is but a vassal for the U.S. for this move is disingenuous at best. After Georgia, Crimea, and now the rest of Ukraine, anyone would make such a decision. Out of their own will. In order to survive.