American soldiers will not be fighting in Ukraine and chance of WW3 is 0.00% McCain’s trying to score some points, trying to compensate for Obama’s weakness.
Ukraine is on her own. They might have the moral support from the West, but it means nothing when facing tanks. The choice for Ukraine: they will fold against Russian aggression, or they will fight. If they fight, only hope of winning is inflicting enough casualties that Russians lose appetite to continue fighting. If they fold and there’s a Russia-friendly government, then resettlements to Siberia and another genocide are not far behind.
If Western Ukraine is threatened, Poland will enter the fray.