The actions of "Israel" is that of a sovereign Settler-Colonial project that acts within its own interests. The US is the world hegemon of Capitalism-Imperialism and its actions are determined by its interests in participating in the global process of capital accumulation. These interests are set forth by the historical process of the development of capital into a global political and economic system.

The stability of the zionist entity's settler colonial project, like that of the early US settler-colonial project, is dependent upon

1. The destabilization of its neighboring region. and
2. The expansion of its territorial borders to include more land for settlement.

The interests of Israel are often encompassed within the interests of global capital (The US being the world hegemon of global capital). This is much the case because the destabilization of Southwest Asia and North Africa allows for the greater penetration of capital into regions that are often seen, from the Imperial Capitalist Class's perspective, as being more impermeable and whose political and economic conditions as being unfavorable for the profitable extraction of materials and the exploitation of labor. Through the process of Israel struggling to attain stability for itself through the practice of settler-colonialism, they are creating conditions that are favorable for Capitalism-Imperialism i.e. favorable for the US regime.

Here we can see how the US and Israel can share material interests. This I am sure we don't disagree on. I hope so far that I haven't given off an air of arrogance in the way I'm setting up my point, I'm just trying to lay a groundwork.

"Israel also literally acts like it’s the senior partner in the relationship. It does whatever the fuck it wants and the U.S. supports it literally unconditionally."

The zionist entity doesn't need to be told to genocide Gaza, bomb its neighbors, and annex territory, just as the US doesn't need to be told to help with the destabilization of Israel's neighbors, the SWANA region as a whole, and the attack on Iran. This is the case because both share material interests and these actions change geopolitical-economic conditions in a way that favor the achievement of said interests for both of them.

In reference to the relationship between the US and Israel, I said it's "ridiculous to say that the zionist entity is the real shot caller." In other words, I am saying that the US is in control of itself and has a greater control of its own power and how that power is being projected into SWANA. This is not a denial of Israel's attempts to sway US policy. Instead, we can see Israel's attempts of swaying US policy, through examples like blackmail, as proof of the US's sovereignty over its own interests and power, for if this wasn't the case than why would Israel being trying to gain leverage over the US in the first place.

"I don’t think the U.S. is the entity choosing to shred the perceived prestige of its military and the legitimacy of its hegemony for a war Israel started."

For the reasons stated above the US and Israel both share the interest of seeing Iran destroyed. Iran, it's existence; resistance; and support of resistance groups throughout the region is a threat to the zionist entity's settler-colonial project. For this reason, Israel wants the destruction of Iran. Iran, its sovereignty and control of its own material resources; its unwillingness to allow western penetration into its own domestic markets; its control over strategic geography that can be leveraged against global capital (Stright of Hormuz); and the fact that, through its exercise of its sovereignty, it acts against the interests of global capital in such a way that makes it a buttress of the formation of a more multipolar world. A multipolar world that would necessitate the reduction of the US's hegemonic control and power of the global order of capitalism-imperialism. It's here that we can see that the US's war on Iran isn't just some war Israel started but is in fact a war carried out by the US for real and material purposes in order to achieve real and material interests.

As far as the US's military prestige and legitimacy being shredded, in my opinion, it is the result of several things.

1. First and foremost, the resistance of the Iranian people in waging this anti-imperialist struggle against the US and Israeli regimes. For it is their struggle alone which acts as the rock that the US's prestige and legitimacy is being dashed upon.
2. The tactics of Iranian resistance and the difference, particularly in the industrial capacity of Iran, that separates Iran from the US's other previous engagements.
3. The US vastly underestimating the sheer extent and ways by which Iran is resisting against its acts of aggression.
4. The decades of neoliberalism and its impacts on the US military's capacity to wage war, especially a war with an industrialized nation that has had decades of experience learning from the ways in which the US has invaded its neighbors in the region.

Edit: Formatting Markdown