I don't what happened. But I cannot download the POI file.
After click the country in the above post, I got the "POI Category: Road Safety in United States" and a list. Then I clicking any item in the list, a page with the green download button show up. No matter I choose a state or not, clicking on the "download" will redirect to a new page with
"GPS POI download format:
Return to the United States or to Safety in the United States".