Maybe? But that's not really his call, that's Constitutional law. The Supreme Court and Congress are not crazy enough to let him get away with it, especially with such a narrow margin in the Senate. Also, not honoring Treasury debts would absolutely kill the stock market and piss off all of his supporters.

So no, it's just fluff.

If you're really worried about it, you can buy corporate bonds, but if government bonds aren't honored, you'd be better off investing in canned food and bottled water, since everything would collapse. If the government doesn't honor its debts, nobody would trust the US dollar since government debt is a major component of money supply regulation (i.e. inflation).

He'd be impeached faster than he can say "MAGA" if he intentionally defaults on our debt.