You have two choices. Either set the default value in the bean data or use javascript/jquery to set the html input text value.
<h:form id="formId">
<h:inputText value="#{bean.cit.nationality}" id="nationality"/>
<script>$("#formId\\:nationality}").val() = "American"</script>
</h:form>
Or you can use a more generic approach to find the client component within its parent or naming container:
$("##{component.namingContainer.findComponent('nationality').clientId}")
You can also use a utility method to escape the JSF colon to reduce conflicts with jquery.
$("(PrimeFaces.escapeClientId('formId:nationality')")