AMNA NAWAZ: Next Tuesday's election results are being closely watched overseas, but perhaps nowhere more anxiously than in Ukraine.

Vice President Harris has promised to continue supporting Ukraine if she wins, while former President Trump has ridiculed the billions of dollars in military aid the U.S. has sent to Ukraine and says he could negotiate an immediate end to the conflict.

Special correspondent Jack Hewson traveled to the front-line town of Kurakhove in the Eastern Donbass region to meet with American volunteer fighters considering whom to vote for and what their votes might need for the war.

ZACHARY JAYNES, U.S. Army Veteran: My name is Zachary Jaynes.

I spent four years in the U.S. Army, where I deployed to Afghanistan three times.

And I have been fighting in Ukraine since March of 2022.

JACK HEWSON: Jaynes and a squad of international fighters gave us access to talk to them about the nature of the war and how it may be affected by the U.S. election.

Like all parties to this conflict, they're being forced to adapt to drone warfare, and today is test day.

ZACHARY JAYNES: So this is just a field we use as a range.

JACK HEWSON: Drone headsets and control pads are increasingly superseding machine guns and artillery in this war.

At this range, just a few miles from the front line, they're testing a kamikaze drone.

Hundreds of thousands of these flying, improvised explosive devices, $500 a pop, are the most effective part of Ukraine's air force.

The contrast with the resources available to Jaynes when he was in Afghanistan is stark.

ZACHARY JAYNES: Being in the U.S. Army, you have every asset available to you.

No question that, if you need something, you're going to get it.

We're flying on Chinooks.

We have as many air assets flying above us as we can, whereas, here, I mean, we're in the trenches.

You're fighting gets done to me that has air superiority.

So the first time you're in a tree line and you hear a jet fly overhead or a cruise missile fly by, it kind of makes you realize that you're the underdog here.

JACK HEWSON: Even magazines for their rifles have at times been scarce.

But, for Jaynes, the differences with Afghanistan aren't just material.

ZACHARY JAYNES: So, even as a soldier there, you couldn't help but shake the feeling sometimes that you are a foreign soldier in fact occupying a foreign land, whereas, here, it's the opposite.

We're fighting with Ukrainians who are defending their homes, defending their families from a foreign invasion.

And being able to be on the other side of that for once, it feels good.

JACK HEWSON: But Ukraine's cause may be threatened by domestic political developments.

DONALD TRUMP, Former President of the United States (R) and Current U.S. Presidential Candidate: I think Zelenskyy is maybe the greatest salesman of any politician that's ever lived.

Every time he comes to our country, he walks away with $60 billion.

I will have that settled prior to taking the White House as president-elect.

(CHEERING) DONALD TRUMP: I will have that settled.

JACK HEWSON: Trump says he can broker a settlement, but Moscow has shown no interest in negotiating peace, except on humiliating terms deeply threatening to Ukraine's long-term security.

The political archetype of Republicanism with regards to international affairs is usually rather more hawkish.

What do you make of the situation where it feels the other way around right now?

ZACHARY JAYNES: Yes, it's a bit strange, but we're seeing again with the America first movement, which is hearkening back to the era of the 1930s and the 1940s of American isolationism in the face of a different fascist threat at the time.

So we're seeing the parallels happening today.

JACK HEWSON: Jaynes is a Democrat, but, like his fellow squad member Call Sign Sturdy, anecdotally, most of the American soldiers fighting in Ukraine are Republican.

Given the noises Trump has so far made on Ukraine, it puts them in a confusing position.

STURDY, U.S. Army Veteran: So I would probably vote Trump, mainly for the isolationist view of, like, America comes first, build America back up, and then we can probably try and help the world again, or whoever else, because it's hard to support others when you yourself are falling.

JACK HEWSON: But doesn't that mean in the immediate term it could greater endanger your life?

STURDY: Absolutely.

But that's my personal risk to choose.

America should come first, but also that I think, in the grand geopolitics, I think it's very vital that Ukraine is like an independent country.

So it is a personal conflict.

JACK HEWSON: How this personal conflict and how the U.S. election turns will be pivotal.

Under renewed bombardment captured here on Jaynes' phone in the days after we left, the squad has now abandoned this drone workshop, as Russian forces continue to advance.

Arriving under cover of dark, headlights off to avoid targeting by drones, we visited an artillery position near the front line 10 miles south of Zach's team.

This is an American supplied M777 howitzer.

For all the drones and improvised tech, the bulk of the battle is still artillery.

But the Ukrainians need more shells.

Dwindling ammunition for these guns has already cost Ukraine big.

After U.S. Congress dithered over its military aid approval over the past year, key strategic towns were lost as Ukrainian guns fell silent.

ZACHARY JAYNES: So, when funding for Ukraine doesn't get approved, that doesn't just stop in D.C.

It doesn't stop in Congress.

That affects everything down the chain all the way to the guy in the trench in the Donbass fighting for his life.

JACK HEWSON: If Donald Trump wins this election and aid is cut off, what would that mean here on the front line?

ZACHARY JAYNES: It means the guns stop working.

They start going quiet, slowly run out of shells, ammunition, medical supplies.

Sure, the European countries can step up and try and fill those gaps, but, in the end, that would basically be the beginning of the death toll for Ukraine.

JACK HEWSON: No one knows for sure what Trump will do if elected, but as the sun sets on November 5, Ukraine's defenders will have a sleepless night ahead of them as they wait for the results on which their survival may depend.

For the "PBS News Hour," I'm Jack Hewson in Kurakhove, Ukraine.