Bernie Sanders and others associated with the DSA have been raising the impact of trade and global financial treaties for decades. Hell, even Ross Perot made "the giant sucking sound" that NAFTA would create a center piece of his campaign. Trump never proposed anything at all that would have addressed the impacts, and hence was lambasted over this. "I will bring back <dying industry>" and then doing precisely nothing (often because there's nothing that could be done) is solid grounds for ridicule.

There may only be a "a few" wedge issues, but they concern the fundamentals of how a society is run and organized. To name just a few in no particular order:

role of redistribution in the economy / role of religion in public education (and education and public life more widely) / whether or not life begins at conception and the moral consequences of one's answer / how much (if any) foreign military intervention / the importance of a mammoth response to climate change / the extent of and response to systemic discrimination in historical and present day society / individual responsibilities during public health emergencies / the roles and responsibilities of for-profit corporations in society / ...

People do not agree about these things, nor will they.