Bernie is doing exactly what US imperialists want him to do. Marx recognized that petit bourgeois politicians weren't the great agent for change rather the international working class are so dividing working class by nationality can delay the coming of international socialism.

Most socialists are protectionist by necessity, due to the realities of nation based democratic institutions.
I get a lot of faux claims about Europe being internationalist and many left wingers are remainers because of it. In reality is a supra-nationalist organisation in the control of a corporate oligarchy.
Both the US and the EU operate protectionist economic policy, as it would be political suicide to offer the same rights and privileges to workers the world over.

But have no delusion about this. Bernie, nor any Euro-socialist party can be confused with National Socialism, as they all promote racial, ethnic, gender and religious freedoms and equalities. All parties aspire to extend rights to all world wide, but duties placed upon them through the office of national presidents require them to legislate economic policy which favours their nation.