The Spanish Central Bank's report is quite straightforward: stablecoins in US dollars account for over 98%, while euros only make up 0.2%. This isn't diversification of currencies; it's essentially an extension of dollar dominance. Fragmented regulation is indeed a real issue.

The Bank of Spain warned in the Spring 2026 Financial Stability Report that widespread adoption of stablecoins could exacerbate currency substitution, expand cross-border financial flows, and amplify cross-border transmission of shocks from U.S. monetary policy and different legal jurisdictions.
The global stablecoin market cap exceeds $320 billion, with USD stablecoins accounting for 98-99%, and euro stablecoins about 0.2%; stablecoins issued across multiple jurisdictions, such as USDC and USDT, may pose risks of regulatory fragmentation and crisis management coordination.