When the US government gets involved in an international issue, they generally give a justification statement. Such as, our national security was threatened by so and so and such and such. As can be expected, they did the same for the current Ukrainian crisis. John Kerry said, to paraphrase, that since international law ensures our national security, and since Russia broke international law, we are thereby threatened by Russia’s invasion of Crimea.
To me this a stretch, while technically it is true, it does not affect us. Our boarders are secure, because of our military’s strength, and through our good relations with our neighbors. Within the last one hundred years, we have only one instance of a foreign nation attacking us with a sizeable military force, Pearl Harbor anyone? No matter the fears that created movies like Canadian Bacon and the original or remake of Red Dawn, there has been nearly zero chance of an invasion from a foreign nation. Of course there was the threat of nuclear attack, but of actual troops invading to take American soil, there hasn’t been any.
There by it is a specious argument.