The fact that there's a major land war in Ukraine, which the US did not start and had no power to prevent, has come at a huge cost. This is true. Given that Ukraine patently was not just going to roll over, and even if the US hadn't supported them, much of Europe absolutely would. I think it's petty plain the war would still be raging fiercely anyway. Most likely Russia would be on the skirts of or in Kyiv and Odessa by now, with a horrible bloody partisan conflict reminiscent of Vietnam or Afghanistan, or a massively scaled up version of the Chechnya war raging throughout the country.

Do you relish the prospect of Russian troops on the borders of Poland, Slovakia, Hungary and Romania? I don't.

Meanwhile US relations with Europe would be at the lowest level since WW2, it would be seen as an utter abandonment and betrayal of our shared values, including US treaty guarantees on the sovereignty and territorial integrity of Ukraine. America's allies across the world would know for a fact the US could not be relied upon to support them. Russia would know this. Taiwan would know this. China and North Korea would know this.

They would also realise that this situation might only last as long as the current administration. There are some in the world that would see this as a golden opportunity.