As I said Finland is not a NATO treaty country and thus not subject to compulsory NATO defense. Any military assistance in case of an attack on Finland will only be voluntary and to be decided individually by NATO member countries, regardless of whether or not the attack on Finland has roped in a NATO member.
The same is true for Japan or Taiwan or the Philippines, etc., in case the US is roped in by mutual defense treaty obligations if any of these countries are attacked.
Do you really think that the NATO under American command won't come for Finland's defense if Russia were to invade them, hypothetically speaking? Finland borders Russia. NATO is hyperventilating at the prospect of an invasion into Ukraine, that has:
a) Been a cradle of Russian civilization, been a part of everything Russian for literally centuries until 1991
b) More than half of Ukraine (barring some parts of western Ukraine) speak Russian as regularly as Ukrainian. c) Nothing to do with NATO or western alliances like since the beginning of European nation states.
Come on buddy, you're not being serious now
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Japan is a different ballgame altogether. NATO is not obliged to defend them but the USA is. Same for South Korea and the Philippines. And if Americans crack their whip, the NATO allies will do as told even in their case.
Economic, commercial, strategic and diplomatic alliances are all-encompassing. F-35 is the pinnacle of American aerospace technology; the finest engine, the finest HMD, the best of stealth and the best of weapons on the platform.
Getting it is not just like a commercial transaction but requires some form of assurances in terms of commitments. US just won't give F-35s to any country that happens to border Russia.