The US may well be a nuclear power but there are seven other acknowledged ones (including an islamic one with a shared land border with Iran), one unacknowledged one which is also involved in this war... and that's just the ones we know about. Its 'huge' military couldn't intervene in the Iran demonstrations in January despite Trump's vague insinuations because its readily deployable power projection assets were floating around off Venezuela, and the current campaign in Iran had to wait for them to move to the Middle East. This same huge military gives the impression of a technological marvel, and it is undoubtedly strong in the air, but it has repeatedly found itself wanting against enemies fighting asymetric wars, living in caves, flying cheap drones, and so on.
The economy is the interesting one, because Presidential legitimacy essentially flows from American consumers. This is a problem because the American consumer is essentially propped by the foreign buyers of US government debt who fund the trade deficit and maintain the US dollar's value by entrenching its position as a global reserve currency. Meanwhile, the stuff American consumers buy to keep the whole show running is utterly interdependent with the global economy, not just on manufactured goods themselves but with the supply chains behind them in energy, materials, minerals, and labour. The US is actually rapidly heading towards a middle-class cost of living crisis just like we have in the UK, caused by many of the same things: declining productivity, increasing dependency ratio, and many, many chickens coming home to roost. It just hasn't really hit middle class pockets yet, although poorer Americans know all about it. If you strip out the Magnificent Seven, the US stockmarket has been flatlining at best for a few years now. Supply side price shocks like what's happened in the last three weeks will cripple the US economy, which will cascade out again through the rest of the globalised world in a vicious circle.
Trump half-recognises some of all this, which is why he is trying to use tarriffs to re-shore manufacturing although his starting point is about blue collar jobs that will vote for him. No serious economist subscribes to his policies, because they don't work in the presence of the global structural realities I've just described. Trump seems taken by surprise every time markets react negatively - and predictably - to his actions, and he seems to genuinely believe that he can control markets and the public by making things up, telling people what to do, and lying to them. Newsflash: he can't, because the US economy is fundamentally fucked and no amount of tinkering from the Oval Office (or Mar-a-Lago) will change that.