Express Mail is a guaranteed service and yes you can get a refund, I've done it. Go to the post office where you shipped the package out of, show them the receipt, and they will have to tell the postmaster there about the situation, which will initiate a letter in the mail to you. When you get the letter you'll fill out a bunch of info, including a copy of the receipt, and bring that back to the same post office and give (have employee give) to the postmaster. Assuming all info they require is provided you should get a refund check in the mail. We've done it once so far, as I just realized this was possible.
The main thing is they ask for a receipt that shows the "guaranteed delivery date" but chances are your receipt won't. That shouldn't matter, as it didn't in my case, they can pull up on a computer what the guaranteed date is for a package shipped on the date you shipped yours, and it will be clear it arrived late. Now....if they 'tried' to deliver the package within the guaranteed time period, but person wasn't home to sign for it, etc, then you're out of luck. I can't believe they would tell you refund wasn't possible.
Also just another note on USPS. I ship stuff all over the country and world with them. Never had a package lost in the USA, and overseas it looks like we have one possibly lost so far, although I know it will show up, even if it's 3 months from now. They are actually quite good at delivering, but when you're talking about shipping internationally USPS loses control of the package when it leaves the country and then you're depending on the local country's postal system, and in many cases their postal systems are horrendous (see Spain). For tracking, yes UPS and Fed Ex will give you best updates. Also, not sure if you guys knew, for Express Mail shipments, USPS has contracted with Fed Ex, this is really the only reason they guarantee anything on Express Mail. Not that Fed Ex delivers the package, but I think the package leaves the post office, gets on a Fed Ex plane, and then reaches the local post office wherever you sent it.