People have hated rich people since the dawn of time, America is no different .
US tax rate is getting more and more in line with Europe, and why wouldn't that be?
Hatred for rich people is something known for centuries now.
Taxes aren't just a way to raise money for federal and local governments, they are also an elegant way which society has to allocate social hatred. You need a corporate tax because people hate corporations, a wealth tax is being discussed and on the horizon because people hate the wealthy, this capital gain tax is on the table because people hate those who make money via capital investment, that's because it's very far removed from doing any work which is perceived as "real work" by the population.