A multi-national company is still responsible to multiple nations in differing amounts though, no? It shouldn't mean "responsible to no one." And America quite clearly should have some significant claim on Google, even if it isn't all of it (or necessarily even a majority). Furthermore, most of the those non-American countries that Google should be accountable to (i.e. most democratic countries and most developed countries... as that is from where it draws revenue and employees) rely, in large part, on the US military for their own national security.
>There's also a real chance that I might get hit by a brick and die tomorrow, yet that doesn't stop me from going out.
This misses the point entirely--which was that whether or not the US military is good or bad for the world is a complicated and difficult question to answer. At the very least, this is clear from the large number of democratic countries who have chosen to mostly rely on the US military for their own national security. So the apparent certainty in the moral correctness of those refusing to work on technology for it is unjustified.
Again, I'm not saying that these employees are necessarily making the incorrect moral decision. I'm saying that the conversations on this topic seem to overlook a lot of the ethical difficulties associated with their choice.