The biggest holder of US debt is...the US. But ok, what choice did China have? If they kept the money at home, it would have collapsed the economy, investing in US treasuries at an effective -3% was the best they could achieve and have some degree of safety. Whatever you think of the US economy, foreigners still have a lot of faith in it. Only libertarians and republicans running for office think this faith is misplaced.
Now, who gets wiped out in a US default? We do the most, actually, but maybe the Chinese and Japanese hurt a bit also. No one is expecting that to happen, and US debt levels are not particularly high compared to the rest of the world.
> Physical, unambiguously owned metal is the insurance, the vehicle that will transition you through to the otherside.
You can't take gold with you to heaven. Ah, you meant the otherside of a collapse. If the economy completely collapses, no one is producing anything of value that they can spare for trade; your metals are still worthless. The law of supply and demand remains, and you just get screwed on supply.
If you really believe in metals, however, I strongly recommend that you move to Australia if you aren't there already. They have the largest reserves, take whatever we have out of the ground now and multiply it by 10. You can just become a miner and become rich, because of course, we can eat gold can't we?