The globalization that allows the wealthy to eliminate their first-world workforce also allows them to avoid just about any tax they don't feel like paying.
Where did you get that from? The wealthiest 1% of Americans alone pay 50% of the federal income tax. The bottom 80% pay only 15%.
Edit: at a 50% marginal tax rate if the 1% get 60% richer through this kind of automation and offshoring, we could lower the tax rate on the bottom 80% to zero!
Edit #2: If the 1% get 120% richer, we could start handing out checks to everyone in the bottom 80% equal to what they're paying in taxes today! See where I'm going with this?
You're confusing wealth with income.
If MegaRoboCo Inc. and their contemporaries are making $1 trillion a year each in 2050, the tax revenues (corporate, capital gains, income on dividends, income on executive compensation, whatever) can be enough to support the resulting mass unemployment.
I'm not saying that everything is fine and dandy, I'm saying that pointing finger to random chicken in the sky and shoot them won't solve the real issue. There are a lot of problems, but American politics right now is a bit engrossed in the wrong kind of trivialities.