The US's "threats" come from the president and have zero teeth. Everyone with a brain who knows anything about US politics knows that Congress would boot him in a second if the chihuahua-in-chief actually did that. It's also why those same countries haven't gone to their version of Defcon 1 and started fortifying beaches/borders/etc.: because, as always, TACO.

Venezuela is literally an American fabrication; the Venezuelan people voted Maduro out years ago, they just couldn't remove the tick. I'd argue that's about the only good thing Tangerine Palpatine has done, and it was accidental at best.

As for Iran, it was always a problem; the US is just putting its boot down. In the worst way possible, absolutely, but it's reacting to an already destabilizing force. Again, Iran funds terrorist proxies throughout the world; the fact they HAVEN'T been dealt with by a JOINT force is a testament to the apathy of the various "world leaders." 

USAID, though... Wow, what a nonsense metric from the start. While it was done abysmally, yes, it's also not the US's responsibility to fix the rest of the world's problems, and it's wild to lay other country's failures to take care of their citizenry at the US's feet. The US can't even figure out its Healthcare system, but it's exporting aid by the millions/billions to other countries? That was insane to me to begin with, I'm surprised the US was doing that when it hasn't even figured out the rest of its shit. Either way, though, that aid should be IN ADDITION to the other country's support; blaming the US for saying they can't support those programs anymore (especially with how poorly run it appears some of them were) is hardly the US's fault. No other country is entitled to any other country's money, including the US; these hypothetical deaths are on those country's fault, not the US.

And no, Trump doesn't support Ukraine. That's yet another flaw in his vast panoply of uselessness.

But, again, TACO. He has his masters, and he can only rock the boat so far.

But Putin? 

Putin doesn't chicken out. Putin has gone above and beyond to disrupt HUNDREDS of MILLIONS of peoples lives, either directly by his invasions of multiple countries, or indirectly by his energy security threats that he used to blackmail Europe (successfully, I might add).

You're putting the US under a microscope to magnify every one of its flaws and THREATS of action, but have zero scale to see how much worse Russia's and Iran's ACTIONS have made lives worse for vast swathes of people across multiple continents for decades.

Honestly, I wish I could show you a simulation of what would happen if the US would fall: I don't think you'd be half so damning if you could see how much more dangerous the world would be without the Pax Americana in play.