<ul id="dropdown2">
   <li>
     <a href="#">AL East     </a>
     <ul>
       <li>
         <a href="#">Baltimore Orioles         </a>
       </li>
       <li>
         <a href="#">Boston Red Sox         </a>
       </li>
       <li>
         <a href="#">New York Yankees         </a>
       </li>
       <li>
         <a href="#">Tampa Bay Rays         </a>
       </li>
       <li>
         <a href="#">Toronto Blue Jays         </a>
       </li>     </ul>
   </li>
   <li>
     <a href="#">AL Central     </a>
     <ul>
       <li>
         <a href="#">Chicago White Sox         </a>
       </li>
       <li>
         <a href="#">Cleveland Indians         </a>
       </li>
       <li>
         <a href="#">Detroit Tigers         </a>
       </li>
       <li>
         <a href="#">Kansas City Royals         </a>
       </li>
       <li>
         <a href="#">Minnesota Twins         </a>
       </li>     </ul>
   </li>
   <li>
     <a href="#">AL West     </a>
     <ul>
       <li>
         <a href="#">Houston Astros         </a>
       </li>
       <li>
         <a href="#">Los Angeles Angels         </a>
       </li>
       <li>
         <a href="#">Oakland Athletics         </a>
       </li>
       <li>
         <a href="#">Seattle Mariners         </a>
       </li>
       <li>
         <a href="#">Texas Rangers         </a>
       </li>     </ul>
   </li> </ul>

In style element (<style>) within head element:

#dropdown2 {
    padding: 0;
    margin: 0;
    list-style: none;
    display: flex;
  }
  #dropdown2  li {
    flex-basis: 15em;
    flex-grow: 0;
    flex-shrink: 0;
    align-self: flex-start;
    padding: 0;
    margin: 0;
    display: block;
  }
  #dropdown2 li ul {
    display: none;
    padding: 0;
    margin:0;
    }
  #dropdown2 li:hover ul { display: block; }
  #dropdown2  li {
    border: thin solid navy;
    font-family: calibri,verdana,tahoma,helvetica,sans-serif;
    background-color: #ccf;
    }
  #dropdown2 ul li { background-color: #eef; }
  #dropdown2 a {display:block; padding: 0.25em;}
  #dropdown2 a:link,
  #dropdown2 a:visited,
  #dropdown2 a:hover,
  #dropdown2 a:active
    { text-decoration: none; font-weight: bold; }
  #dropdown2 a:hover { background-color: navy; color: #ccf; }