The dropdown sub menus for underscores.me by default align left.
If you need to change it to align right, go into style.css “# Menus” and change the following lines:
.main-navigation ul li:hover > ul,
.main-navigation ul li.focus > ul {
left: auto;
right: 0%;
}
.main-navigation ul ul li:hover > ul,
.main-navigation ul ul li.focus > ul {
right: 100%;
}