# change_form.html
Добавил этот блок практически в конце html файла.
{% block javascript %}
    <script src="{% static 'admin/js/vendor/jquery/jquery.min.js' %}"></script>
    <script>
    $('#id_region').change(() => {
        let region = $('#id_region').value;
        console.log(region);
        $.ajax({
            type: 'post',
            url: 'ajax/load_points/',
            data: {
                region: region,
                csrfmiddlewaretoken: '{{ csrf_token }}',
            },
            success: (data) => {
                console.log('hello');
            }
        })
    })
    </script>
{% endblock %}

# route_admin.py
class RouteAdmin(admin.ModelAdmin):
    change_form_template = "admin/telegram_bot/route/change_form.html"

    def get_urls(self):
        urls = super(RouteAdmin, self).get_urls()
        urls.append(
            path(
                "ajax/load_points/",
                self.admin_site.admin_view(self.load_points),
                name="ajax_load_points",
            )
        )
        return urls
    def load_points(self, request):
        print(request)
        data = {'points': ['test', 'test2'],
                'opts': Route._meta,
                'change': True,
                'is_popup': False,
                'save_as': False,
                'has_delete_permission': False,
                'has_add_permission': False,
                'has_change_permission': False}
        return render(request, RouteAdmin.change_form_template, context=data)