If I hurt any Biden supporter during my last post, please accept my apology. As an non-American, please also understand I am not that deep into the game of pro or anti-Trump or pro or anti-DP agenda.
The real problem is, Russian aggression was there for decades. Ukraine is not the first victim, Georgia is.
https://en.m.wikipedia.org/wiki/Russo-Georgian_WarBack in 2008, well Georgia was mickey mouse country and at that time George W. Bush and Dick Cheney were in the white house. They let go, say a few words and split a portion of Georgia into an unrecognized South Ossetia.
Then there is Crimea in 2014, and now.
As you can see the appetite of Putin will just get bigger and bigger, while we are all waiting him to go to a better place than Earth, but his successor can simply pick up the plan and go on.
While some of us have mentioned the sanction, the consequence is now weaker than before as there is another option called PRC. The scale of economy of China has grown in 15 times in between 2000 to 2021, so while US's sanction can cover most of the countries spending USD, Russia is not so isolated from the world economy besides the gas deal. Or to go further, even if EU cut ties of with Russia, they can still do business with China to stay alive.
And for what USA can do to stop Putin, I would suggest them to take lessons from ...... China, while in a good way.
https://en.m.wikipedia.org/wiki/Stealth_War:_How_China_Took_Over_While_America%27s_Elite_SleptGeneral Spalding has mentioned a book called "Unrestricted warfare", which was written by PLA strategist in 1999, to give advice to China on how to fight silently against USA without bloodshed. Technology, economy, intelligence, propaganda and lots of other non-military actions can be useful.
Finally, I was saddened by the fact that some of posters above would think that my stance is for American soldiers to lose their lives for Hong Kong. No, never in the world I would think in this way. Even for how much I love this place, I am still alive and not leaving, unlike many of my friends and relatives. They chose to give up and start a new life elsewhere. I am thankful for the democratic world like UK, Canada and Australia to absorb them as immigrants.