In sake of readability it should be something like
<?php
$countries = $myaddress->get_countries();
foreach($countries as $value) {
$selected ='';
if($value=='United States') $selected ='selected="selected"';
echo '<option value="'.$value.'"'.$selected.'>'.$value.'</option>';
}
?>
desire to stuff EVERYTHING in a single line is a decease, man. Write distinctly.
But there is another way, a better one. There is no need to use echo at all. Learn to use templates. Prepare your data first, and display it only then ready.
Business logic part:
$countries = $myaddress->get_countries();
$selected_country = 1;
Template part:
<? foreach($countries as $row): ?>
<option value="<?=$row['id']?>"<? if ($row['id']==$current_country):> "selected"><? endif ?>
<?=$row['name']?>
</option>
<? endforeach ?>