This graph measures the share of income held by the top 1%, and the solid black line is America -- which is moving on trend with other countries.
This chart makes the following "correction" -- it assumes that the rise in reported American income after 1986 can be attributed to the 1986 Tax Reform Act, which sharply reduced marginal tax rates, and resulted in a sharp rise in self-reported income. Winship wants to interpret this result as a permanent shift in reported income. However, if you look between ~1983-1998, it looks like a fairly clean linear trend, with a temporary spike around 1986. There is also a small drop in reported labor income to evade the 1993 tax hike. It's possible that the 1986 tax reform only resulted in a transitory rise in reported income; certainly this is the argument in Piketty and Saez, where the US data comes from. Without that correction, the US becomes a slight outlier in terms of top income share.
Regardless, this data seem to support the idea that dynamics are very different within the Anglosphere and elsewhere. Canada, America, the UK, and Ireland all saw a sharply rising share of top 1% income in the past few decades. Countries like France, Germany, Sweden, and Japan also saw rising inequality, though not to the same degree. This points to winner-take-all dynamics operating within the large linguistic zone of English-speakers, as top talent moves smoothly between these countries. It's also notable that several of these countries have seen seen a comparatively greater role of Finance in recent years. From a paper by Reshef and Philippon:
It's telling that the drop and rise in relative wages in Finance mirrors the experience of top income inequality for the US as a whole. It's interesting to think through why the presence of the financial sector would alter income distributions for whole economies around the world. One explanation is that the role of leverage and arbitrage allows a select group of highly-skilled managers to concentrate a far greater share of income. Another possibility is that this reflects the role of opaque markets, information asymmetry, or some broader mispricing that is penalizing the real economy.
Another set of arguments this take on are those (ie, like that by Rajan) that argue for a causal role of income inequality in fueling the recent financial crisis. If instead inequality was broadly rising around the world, it becomes a more complicated story why the crisis began here.