WASHINGTON: Border restrictions were being tightened around the world on Monday in the face of an unrelenting coronavirus threat, after a weekend in which anger at social distancing rules bubbled over into fiery clashes in the Netherlands.The United States was set to join France, Israel and Sweden in pulling up the drawbridge to certain arrivals, with special concern about new strains of the pathogen that originated in Britain and South Africa."It’s up to us to show that we are...