Why is the consulate refusing to grant my extreme hardship waiver?

There could be a number of reasons that your I-601 request for a waiver of inadmissibility hasn’t yet been granted, but here are the main ones that pop out from your letter:

• ** You attempted to prove extreme hardship to the wrong person. You, as the visa applicant, are all-but irrelevant in this application. It’s extreme hardship to your wife, as the U.S. citizen, that counts toward this waiver request. She should be the one writing a letter explaining how she will suffer if you are denied the visa. Fortunately, it looks like she has some grounds upon which to claim extreme hardship, namely that she would lose her livelihood and be separated from her elderly mother. Note that separation from one’s spouse and financial difficulties aren’t sufficient by themselves to amount to “extreme” hardship, but they can be worked into the analysis. For example, if you were a primary source of emotional support to her while in the U.S. during this difficult time caring for her mother, and she can get a letter from her therapist saying that she is already suffering in your absence, that will help.
• ** You didn’t submit evidence in support of your application. It’s not enough to claim extreme hardship (to your U.S. spouse, remember) — you must document as many portions of this claim as possible. So, for instance, you’d want to provide a letter or medical report from your mother-in-law’s doctor explaining her physical state and need for care from her daughter (your wife); proof of where your wife works (such as an employer letter and pay stubs) along with evidence that such jobs don’t exist in Belgium; and any other documents relevant to proving the hardship your wife would suffer if you were denied the visa. Don’t forget to be specific about what would happen if she moved to Belgium, such as having to sell her home (perhaps at a loss) and find housing for her mother.
• ** You come from a first-world country. Unfair though it might seem, it can be easier to prove extreme hardship if the visa applicant is from an underdeveloped country where the U.S. citizen would face health, financial, and other difficulties to which he or she is unaccustomed. Obviously there’s nothing you can do about this except realize that you won’t come off as very convincing if you spend a lot of effort trying to convince the consulate that your wife would suffer if she had to live in Belgium.

Don’t give up – the letter from the consulate means you still have a chance to prove your case. But you were likely given a deadline to act, and should make sure to provide a full package of convincing documentation within that time. Getting help from an experienced U.S. immigration lawyer is your best bet. For more information, see Nolo’s articles on “Inadmissibility and Waivers.”