It doesn't matter when it was "invented." The fact remains that the United States is an actual country with a government and well defined borders. The country of Palestine never existed. It's a fiction.
The state of Palestine does exist right now. The US government simply refused to recognize its existence.
How long do you think the "state of Palestine" would continue to exist if the U.S quit sending them money? Can they support themselves? Do they have a plan to take care of their citizens?