Wall Street’s quiet corner is making noise again. While the bond market is typically seen as slower moving, it can pack a heavy punch when it’s alarmed. And right now, it’s getting worried about how much more Washington is preparing to pile onto its spiraling mountain of debt because of its desire to cut taxes.

U.S. markets are also reacting to the passage early in the House on Thursday of the Republicans’ multitrillion-dollar spending bill, which aims to extend some $4.5 trillion in tax breaks from Presiden...