Script to set a default country code in a donation page. See https://salsasupport.zendesk.com/entries/23475564-Set-a-default-country-for-a-donation-page.

default_country_code.html

<!-- BEGIN script to change the default country code and save a selected state value. -->
<script type="text/javascript">
  document.addEventListener("DOMContentLoaded", function () {
    var state = document.querySelector("select[name=State]");
    var savedState = (state !== null) ? state.value : null;
    var country = document.querySelector("select[name=Country]");
    if (country != null) {
      if (country.value == "") {
        country.value = "US";
      }
      country.addEventListener("change", function() {
        if (state != null && savedState != null) {
          state.value = savedState;
        }
      });
    }
  });
</script>
<!-- END script to change the default country code and save a selected state value. -->