There literally is a point where you can't spend the money fast enough (on objects for personal use) to lose it. You can lose it doing dumb things in financial markets or with a business, but if you have $3 billion dollars it is impossible to spend it fast enough to lose it. You can burn $40 million down to see (see: most musicians and athletes), but not $3 billion.

Even earning 2% interest on 3 Billion (i.e. Treasury bonds or something nearly risk-free), you can make $165,000 A DAY.

So buy 3 cars today, and tomorrow, and the day after that, and the day after that. You just can't do it.

So whats the difference between $2 billion and $3 billion? Not all that much. (And I don't believe he is avoiding a billion dollar tax bill, he still has to pay some level of exit tax).

But the difference between being able to come to the US and not coming to the US is significant. What if he wants to go to a movie premiere in LA, or skiing with friends in Aspen, or going to Warren Buffet's annual investors meeting, or seeing a VC in Silicon Valley? You can shop anywhere, you can vacation anywhere, and you can eat anywhere. But some events only happen in one country or another. Some partnerships only happen in one country or another.

That's obviously assuming the IRS decided he renounced his citizenship for tax reasons and he is banned from the US.

So, if the US government cares, this person could be denied entrance to the US.