Sure, the US strategic goal is to dominate the world militarily. It could achieve that with half its military spending, arguably even a third. And yes, lobbying

Sure, the US strategic goal is to dominate the world militarily. It could achieve that with half its military spending, arguably even a third. And yes, lobbying can heavily skew what ends up being prioritized, to the point of inefficiency. This is not to say there are not other sources of inefficiency too - the items in which the US spent the most money in the past 20 years have been completely pointless wars that dragged on forever and ultimately achieved nothing. Feeding more money to this largely inefficient (and harmful) machine cannot be justified solely on the basis of increased competition from other countries. Lobbying also works against efficiency by prioritizing older companies over newer, more innovative ones. Look at the progress of SpaceX vs the the ULA. Following your premise that heavy investment can create a scenario where competition will suddenly cease to exist, this type of thing should not be possible. Heck, until World War II the US was not even among the highest military spenders in the planet. It was the heavily militarized Europe that started a conflict and shot its advantages on the foot. So, your premise that you can just overspend your way into invincibility is not sound either, if anything the opposite might happen.