His goal is not to compete with the other two parties and try to become the boss of the White House. Because it is not easy, and it will take decades for his party to mature and be able to compete directly with the Democratic and Republican parties. His goal is for the America Party to win a few seats in Congress, 5-6 seats in the Senate and 8-10 seats in the House of Representatives.
If you follow US politics, most important bills passed in Congress are usually decided by very close votes, and Elon's goal is to use his party's votes to oppose bills that he thinks are pointless.
OBBBA passed the Senate 51-50, the House 218-214, and what if the Elon party wins some seats in Congress? That's Elon's goal.
True, but in order to get any seat, you have to win states, and that won't happen. Nobody has done it, and Elon won't be an exception to this rule. No matter how much money he spends, he won't get anything. The political system of the US is built like this, and no matter how crucial the votes are, they are between two parties and that will never change. At least not this way and not from Elon.