A clean and semantic way to do it would be with CSS.
First, the PHP:
<div class="entry-meta">
<span class="term-links">
<?php foreach ( get_the_terms( $post->ID, 'region') as $term ) : ?>
<a href="https://wordpress.stackexchange.com/questions/233793/<?php echo esc_url( get_term_link( $term->term_id ) ) ?>">Region: <span class="<?php echo $term->slug ?>"><?php echo $term->name ?></span></a>
<?php endforeach; ?>
</span>
</div>
Next, the CSS:
.term-links .usa {
display: inline-block;
width: 16px;
height: 11px;
background: url('http://i.stack.imgur.com/B2K4X.gif');
text-indent: 100%;
white-space: nowrap;
overflow: hidden;
}
Just repeat the CSS for each region, changing the background URL.