Germany, England, and France. As each nation is a member of NATO (North Atlantic Treaty Organization), the US has promised to deliver military aid if they have been invaded or attacked by another nation. So, the United States would send extra troops overseas to assist current groups stationed in Europe. In times of peace, it is most typically economically, but sometimes, US presence in times of increasing hostility is enough to cause the aforementioned hostilities to cease. In both times of war and peace, these nations should assist in the same way as the United States does.