The US federal budget is 3.7 trillion. The president probably can't meaningfully affect the spending of most of that, but his impact is still significant. If I had to ballpark it I'd say a trillion over 4 years seems likely. Plus his long term effect on the nation through laws and regulations.
How many Americans vote? About a hundred million? So the average value of a vote is in the area of $10,000. That is a lot of money. Sure it is much less if you live outside a swingstate, but not by a factor 100k.
Even if your non-swingstate vote was meaningless there is still a tragedy of the commons. If every California Democrat stayed home because the Democrats will win California anyway... they won't. The rational solution to a tragedy of the commons is not to defect.
So the average value of a vote is in the area of $10,000.
That's a meaningless phrase. You want to buy my vote for $10,000? No? Who is going to buy it, then?
Not to mention that when you're calculating "affecting spending" you need to look not at the total number, but at the marginal difference between Hillary and Trump plus weight that difference by your values.
The rational solution to a tragedy of the commons is not to defect.
In which way is it a rational solution if you're the only one doing that?
If there's such a small chance of your vote making a difference in the election, you should be comfortable voting for trump.