That’s not how this works. You made a statement, now back it up.

You are aware that Trump has _not_ stopped this war right? He has floated certain some possible agreements with Ukraine, but his terms have not been agreeable to the Ukrainians. If Trump actually wants Ukraine to come to an agreement with the US, he'll have to come up with a deal that is acceptable to them.

So yeah up until now Trump has done _nothing_ to stop this war. He's really only proved to all the US' supposed allies, that the US is not trustworthy. At this point, Trump should just shut up and stop pretending like he's trying to reach some peace agreement. He should just stop sending funds to Ukraine as he obviously wants to do and just leave the discussion because he's really no longer relevant.

Why is it the responsibility of the US to single handedly stop the war?

We don’t know what Harris would or wouldn’t have done. But we know that what Trump is doing is not going to end up well for Ukraine.

Dealing directly with Russia as if it was up to the US to decide for everyone else isn’t just callous, it’s extremely dangerous.

The Russian economy still can cave in. The war isn't over.

Sure, but at this point it seems like Trump will soon start to actively support the Russian economy.