More than a century of incredibly close partnership and interdependence thrown away for nothing more than stoking American egos, looking for an easy target to bully.
The ugliest part of all of this is that if voters completely reject Trumpism in 2 or 4 years and go back to a sane path, they won't have done it because they were convinced of the gross immoral capriciousness of the Trump administration. The only reason American voters would reject Trumpism is if they decide he's bad for business, and caused serious economic harms.