So remember all the times the EU has been called a 'protectionist racket' by those most strongly advocating Brexit. A new study shows EU countries are in fact some of the most open to trade in the world - but the US is not... 
Now I've only had a chance to have a quick glance at the methodology applied to the Trade Barrier Index (tradebarrierindex.org/about) but it seems relatively robust - covering tariffs, non-tariff barriers, facilitation through trade agreements and more.
Further bad news on the US front - they don't significantly open up their markets in any trade deal. So in swapping full access to the EU market for little greater access to the US market UK companies will overall be disadvantaged in trade terms
And yes, get the sovereignty argument on Brexit, this is specifically targeted at those who make the economic argument for Brexit, and particularly for no close EU relationship in the future. The evidence is very much against them.
