I ended up getting this figured out.The fix that worked was having two if statements rather than an if/else statement. I used a simple variable to help with getting the template i needed.
<?php
$banners = get_field('new_banner');
$uri = $_SERVER['REQUEST_URI'];
$host = $_SERVER['SERVER_NAME'];
?>
<?php
$match = 0;
foreach($banners as $banner){
$banner_match = $banner['full_value'];
if($uri === $banner_match){
get_template_part('templates/frontpage', 'masthead-alt');
$match = 1;
}
}
if($match !== 1) {
get_template_part('templates/frontpage', 'masthead');
}
?>
