The OP question is too narrow. Russia is a major threat to Eastern Europe, much of which is now in NATO or the EU or is aiming to join in order to maintain their sovereignty and develop their economies. It is in our and everybody’s interests that they succeed in truly joining Europe, establishing Western European democratic norms, ending gross corruption, etc.
Putin is also a threat to Russians themselves. His military invasion of sovereign Ukraine is not only a bloody threat to it and eventually to other Black Sea states like Georgia, it is bleeding Russia and the ethnic minorities in the Russian Federation. It has created a challenge to the world order and liberal capitalist democratic states everywhere.
Many developing countries are understandably suspicious of U.S. motives and wish to trade freely with all, including China and Russia, and so do not want to be forced actively to take sides. But it is ultimately in their interests too to develop government institutions and economic systems that guarantee individual rights.
Putin is crystal clear he is in a cultural and political war with the democracies of the West and U.S. in particular — though many Americans — following Trump — think this is all a misunderstanding and really Putin is a “good guy” who has been provoked by NATO.
Americans are now so crazed by domestic ultra-partisan madness, they may actually elect a man who truly admires Putin. So the real threat of economically poor and culturally dead Russia to the U.S. … is that we may destroy ourselves and the best aspects of our own Republican tradition. We may end up mimicking other populist “democratic strongman” regimes … on the road to something worse.
We are in fact failing our own best traditions, and if we abandon Ukraine it will be not just dictator Putin’s victory over Ukraine, it will be a victory for all enemies of America and the very idea of liberal democracy. All the world’s one-party dictatorships, from the one in the Kremlin, to the one in Beijing, to the Mullahs autocracy in Iran to North Korea will celebrate. Our developed mainly democratic capitalist allies will waver and fear for their own futures.
The world will become incomparably more dangerous, and our position in the world much weaker. For the most part, however, it will not have been Russia or Putin who did this, but we Americans ourselves.