In the ongoing struggle between UK Prime Minister Boris Johnson and EU negotiators over the terms of Brexit, Johnson’s backup plan has consistently been to seek increased trade with the United States should a no-deal Brexit stifle trade with the EU. Despite President Trump’s fondness for Johnson, however, a 54-member Congressional caucus now threatens to block any such trade deal if Johnson continues with current plans to scrap the Irish backstop and threaten the Good Friday agreement between the UK and the Republic of Ireland. The Friends of Ireland caucus,…