And trust me, I don't need an Investopedia reference to know the difference between interest rate and yield.
They are two distinctly different things.
I don't know what the interest rate is on the Greek 1 year but I doubt it's anywhere close to 100%. A normal interest rate combined with a crazy high yield like 100% means that the value of this bond has fallen to almost nothing.
Actually, it is pretty simple to figure out. It means the value of a note with 12 months to maturity that has a yield of 108% is currently selling for somewhere around 42 cents on the dollar.
Since the OP didn't post a link to the site where she got the screenshot, and I was unable to find via several Google searches a similar graph, I have no idea whether or not a Greek 12 month note carries a coupon. It is highly unlikely it does, as damned few bonds of such short maturity do. As a consequence, it is what is known as a "Zero Coupon Bond" and that means it is sold at a discount to its face value, matures at its face value and the difference is the yield. Zero coupon bonds do not pay interest, as there is no coupon rate and therefore no coupon (interest) payments.
This is happening on the secondary market, NOT at issuance. If the trend continues, the Greek government will either issue such paper at 50% of its face value to come closer in line to what the market is bidding existing paper at or they will stop issuing such paper altogether.
Whether or not your or the OP's prediction of yield on US Treasury
12 month paper getting to 108%....well......not bloody likely.
But hey. I suppose it could happen. I hope I'm dead when it does, because we'll be well and truly fucked long before it ever got to that point.