The United States would utterly destroy them and any other country (except mayyybe China) in an outright military battle. Like it wouldn't even be close. No help from Ukraine needed.
We have 11 aircraft carriers here in America. No other country has more than 2 aircraft carriers. Our military dwarfs other militaries both technologically, financially, and in sheer power. Just spitballing but I bet we could probably reduce our military strength by 50% and still beat almost every country in the world.
We struggled with asymmetrical guerrilla warfare back in Vietnam so that could be a problem but in a head-to-head battle like world war II, we're unbeatable. I'm also assuming they've advanced quite a bit in knowledge/technology of taking on asymmetrical geurilla warfare nowadays.
However, the massive force equalizer is Russian nuclear weapons and I don't see Ukraine getting rid of any of those.