I am thinking some fresh ammo might not be a bad purchase.Nope can't imagine it. They may try to do something via Alaska but then they would have the whole might of the US, Canada the UN and NATO to deal with.
And to quote Yamamoto, "You cannot invade the mainland United States. There would be a rifle behind every blade of grass." Even he knew that his navy could only hold us off for a year, then he was toast.....which happened anyway.