The American version, currently, is just like the U.K. version except it doesn’t use embossed numbers - it uses printed numbers which are on the rear of the card.
The front of the card only includes the Chip, contactless logo, Mastercard logo, and the word debit alongside the distinctive Monzo wordmark.
It think that would be a decent refresh of the design, although the concept above looks great too and might be better in the longer term as most banks seem to be going portrait now.
Edit: Found it!