Russia invaded Ukraine on false pretexts with the intent to use military action to overthrow a democratically elected government after their last attempt at coup/puppet government failed when their patsy fled the country after his failed attempt.

After the US failed to act in 2014 despite evidence of Russia starting proxy wars against Ukraine and annexing land illegally, and further muddied by Trump's attempts to withhold defense aid packages he was obligated by law to deliver.

So yes, US involvement has been justified and Ukraine has not only been happy for the assistance but requested more to ensure their freedom and prosperity doesn't vanish tomorrow with Putin's intent to rape the entire country.