re: How does the U.S. or any other country have the right to seize Russian property

Same (and only) right every government has: right of might. The probelm is that when you operate this way you create a culture where everyone operates the same and people stop wanting to do business with you and you lose credibility. That being said, while we are wrong in our actions, probably, Russia is an aggressor and literally doing the same right now on a national scale and likely warrants some punitive retaliation.