Would tourism explode? What would that mean for the environment?
What about international business?
Would it be the end of remote workers? Or would it encourage even more distributed workplace?
In some parts of the world you can live on $5 a day, in others it's $100 - but with cheap travel, those earning lots would buy services in the cheaper places - increasing prices.
And those earning little would seek employment elsewhere, reducing wages.
The overall result would be to flatten the income disparity about nations. (But it would have no effect on the disparity within nations, since that is caused by differences in intelligence, and that won't change.)
Some places would of course "cut themself off the grid" (like North Korea), but the majority would not, and the world (or at least the connected places) would become much more similar.
And some counties would put up barriers (like those separating the US and mexico - if not for those the wages in the US and mexico would tend to equalize, but they don't because of the barrier).
All this assumes that the travel is cheap - if it's expensive, it doesn't much matter that it's fast.
He's saying that local effects of a nation would quickly be brought up to par, whereas the distribution in nations wouldn't likely change.