Thankfulness is pretty equivalent to being poor in spirit. "The poor use entreaties, but the rich answer roughly" (Proverbs 18:23), an example being Nabal of Carmel in 1 Samuel 25. You're not too anxious to be exacting against others when you're aware of being cut a whole lot of slack yourself. Yes, indeed, if you're big on others measuring up, you're rich in spirit. From the standpoint of the gospel, you're in real trouble.
I'm not comfortable with the Thanksgiving holiday. It's based on a fairy tale, that godly people came here and prospered through God's blessing. In fact, they prospered through plague, robbery, and murder, and they were very spiritually proud and self-righteous people. Like the Pharisees, they were full of zeal for God, but they weren't careful to humble themselves. They proclaimed their own righteousness compared to everyone else in the whole world, and - putting light for darkness as Isaiah expressed it - they actually made of this spiritual pride virtue, instead of the spiritual rot that it was. They and we that have followed in their paths have actually given thanks not to God but to our own nets (Habakkuk 1:14-16), by which we have raked in wealth at the expense of the dispossessed Indians, black slaves, and now the rest of the world. As George Kennan helpfully explained in 1948, we had 50% of the world's wealth and 6.3% of the world's population, and maintaining that disparity was what our foreign policy had to be all about. And behind all the blather about democracy and liberty in the years since, that has been what it has been about, so that what the empire has been doing all this time to the rest of the world has now come home to the American people as well.
Thankfulness is perverted when we profit illicitly and then thank God for our ill-gotten gain. That really is taking the name of the Lord in vain.
However, God makes his rain to fall on the evil and the good, and his sun to shine on the unjust and the just. So God gives to the oppressor and wrongdoer his food and drink as well. It's just defiling and shameful to get through violence what we could have received with gratitude, and with no curse added to it. That way we don't have to lie to ourselves and others about how it really was and is, so we don't have to be so brazen and self-righteous.
Sun Tzu wrote in The Art of War that if you know yourself and you know your enemy you will not meet disaster in 100 battles, whereas if you know neither yourself not your enemy you will be defeated for certain. It may take a while. It was so for Assyria, for instance. But it does eventually work out as Sun Tzu taught. When it's important for us to believe that we are righteous, self-knowledge is not possible. Once we have to believe we are righteous, so that everyone against us is wicked, knowing our enemy is not possible either.
So the Thanksgiving holiday should be a time to reflect on our true condition, our real history, how we've actually come to be where we are. Then we can give thanks for something real, that if we face the truth about who we really are and what we really do, grace is available.