With measures announced in early November, Belgium no longer accepts the US CDC card for entry to restaurants, bars, museums, or any indoor venue, other than shops or for take out.
You can get a QR code online (mine took about an hour to get) by going to: https://coronavirus.brussels/en/belgian-cst-for-foreigners/
You will have to download the Belgian CovidSafe App.
Two cautions: First, when you take photos of your passport and CDC card, use a lower quality photo setting to reduce file size, and two, They ask if your document has a watermark, say yes, the CDC symbol qualifies as a watermark.