It's very easy. Putin is a dictator and the Russians have no democracy, undermine others, poison people, etc. The U.S. doesn't have clean hands, but there is no comparison.
As for your other two issues, the US has had no issue undermining elections for years, and runs a public assassination program in addition to anything that remains secret. There is a comparison, and both sides are awful.
Yes it does. Democracy (the concept) is moral because it gives self-determination and liberty to people. Of course, everything, including democracy, is very imperfect in execution.
> the Russian election. And though they're obviously rigged, the US one isn't some glorious opportunity for the will of the people to be heard either.
Again, there is no comparison. It's like saying Hitler and the U.S. both used internment camps in WWII, therefore they are morally equal.
>Again, there is no comparison.
Yes, there is. On basic principle, the choice between two is not far better than one choice. Beyond that, some of the things done to rig American elections are worse than what Putin does. For example, in 68 Nixon interfered in Vietnam peace talks to ensure election. What would have happened without that is unclear, but it potentially cost hundreds of thousands of lives.
The US looks great when compared to Stalin era USSR. When compared to modern day Russia, it's hard to argue we have the unquestionable moral high ground.