The US used to tax capital gains at higher rates, but when they did they also had generous exclusions (IIRC, the first 50% wasn’t taxed)
Why would it? I mean, it wouldn't affect the fair value of companies... just the amount of actual cash you get out of selling the price (and if only gains are taxed, the tax is proportional, meaning that you it can't tax profit into loss, only profit into less profit).
From my (EU citizen) POI, please go ahead. This will help Europe greatly as it's the most rational place to move assets for most Americans, with many great places with great tax and business culture + these are really nice places to live in, actually. That will in turn raise EU wages to the likes of the USA - thanks!
On the other hand we provide corporations unique legal benefits, from which as a shareholder you benefit, it is reasonable for them to have a unique tax regime.
Didn't find that in the article but it's probably along the lines of : the stock market would plummet like a rock otherwise, also real estate. And everyone's net worth is tied up in those asset classes.