Until other people, then the government, figure that out. Like all physical property, it’s only as safe as the amount of force you have and are willing to use to defend it.
The Mandibles, by Lionel Shriver, is a novel that explores the scenario of a debt default by the United States. The resulting currency collapse and social breakdown. Physical property is one of the first things transferred from the weak to the violent, when things start to unravel.