public class HAPI_callOut {

    public List<HAPI_TerrByCount_wrapper> wrapper {get; set;}

    public void deserialize() {

        HttpRequest request = new HttpRequest();

        request.setEndpoint('callout:HAPI_CallOut/territories-by-country/US');
        request.setMethod('GET');
        request.setTimeout(120000);

        Http service = new Http();
        HttpResponse response = service.send(request);

        wrapper = (List<HAPI_TerrByCount_wrapper>)JSON.deserialize(response.getBody(), List<HAPI_TerrByCount_wrapper>.class);
    }
}

public class HAPI_TerrByCount_wrapper {

    public class TerritoriesByCountry {
        public String territoryId {get; set;}
        public String territoryName {get; set;}
        public String startDate {get; set;}
        public String endDate {get; set;}
        public Integer recordIndex {get; set;}
    }

    public List<TerritoriesByCountry> terrByCountList {get; set;}

}

<apex:page controller="HAPI_callOut">
<apex:form >
    <apex:pageBlock title="Alignment Territories By Country Data">
        <apex:pageBlockButtons >
            <apex:commandButton value="Get Data!" action="{!deserialize}" reRender="TerrByCountBlock"/>
        </apex:pageBlockButtons>
        <apex:pageBlockSection id="TerrByCountBlock" columns="1">
            <apex:repeat value="{!wrapper.terrByCountList}" var="territory">
                    <apex:pageBlockSectionItem >
                        <apex:outputLabel value="Territory Name" for="territoryName" />
                        <apex:outputText value="{!territory.territoryName}" id="territoryName" />
                    </apex:pageBlockSectionItem>
                    <apex:pageBlockSectionItem >
                        <apex:outputLabel value="Start Date" for="startDate" />
                        <apex:outputText value="{!territory.startDate}" id="startDate" />
                    </apex:pageBlockSectionItem>
                    <apex:pageBlockSectionItem >
                        <apex:outputLabel value="End Date" for="endDate" />
                        <apex:outputText value="{!territory.endDate}" id="endDate" />
                    </apex:pageBlockSectionItem>
            </apex:repeat>
        </apex:pageBlockSection>
    </apex:pageBlock>
</apex:form>