Not "Is breaking". Has broken.
Trump's ambush on Ukraine and his attacks on Denmark (and Europe in general), Canada, and Mexico have destroyed literal centuries of diplomacy. And after everything we've seen in the past 8 years, other countries have every right to say that American policy has a 2 year (at most) shelf life before being subject to the whims of whoever wins the elections, and any incoming administration can be expected to ignore or outright break the treaties of previous administrations -- including (as we saw with Canada) treaties that they themselves negotiated. All American contracts and treaties come with an extra clause saying that they can and will unilaterally alter or break treaties at any time, for any reason.
Even if Democrats win in 2026, it won't matter because Trump will simply veto any attempts at fixing what he broke. Even if a Democrat wins in 2028 and spends his entire term going on a Trump Apology Tour, what other leaders are going to want to put their trust back in the US when there's a real chance that a Republican congress will come in and gum up the works in 2030? Or a Republican will come in and shit all over everything again in 2032?
Businesses need long-term stability. World leaders need long-term stability. Stability that can be largely expected to carry from one administration to the next, even if the finer points vary slightly. They don't want to do business with someone who's likely to openly break a treaty before the ink is even dry. Especially someone like Trump, who's entire business history has been nothing but him making a deal, then unilaterally breaking the deal, forcing you to the negotiating table to accept a worse deal if you want to end up with anything at all after you've already honored your commitments, and then just stiffing you if you don't accept his lopsided terms. Trump just did that to Ukraine. Trump just did that to Canada and Mexico. Why the fuck would any other world leader trust the US ever again after we re-elected this guy?
These relationships will take decades to rebuild. The US will lose significant amounts of influence and soft power in the process. And that's assuming that we can ever get it back at all. We can't even tell the world that this is the actions of one man that doesn't reflect the values of the people, because we already saw what this man had to offer once. We had 4 years of it. Then 4 more years of him saying he was going to be re-elected so he can do exactly what he's doing now. And we voted for him anyway. Trump said he was going to take a giant shit on our allies, and we collectively said "Yes, please." The rest of the world has the absolute right to listen to the American people trying to apologize for this man and respond by telling them "You voted for this. You voted for him. Go fuck yourselves. Elections have consequences."