For the first time in polling history (since 2000), less than half of Americans say they are “extremely proud” of being an American. Before Donald J. Trump became the Republican candidate for Presidency, that figure had never gone below 54 % (“extremely proud”); it is now 47 %. The figures show equivalent declines among Democrats and “independents”, but a slight uptick among Republicans.
The conclusion is that President Trump makes a net 7 % of the country more ashamed to be an American. I cannot find another President of whom historians say that he made a large proportion of Americans more ashamed of their nationality.