On a scale, how much do you trust your fellow countrymen from the bad parts of town not to rob you? Then how much do you trust your politicians not to lie to you? Then how much do you trust other countries' politicians not to invade you?

There's your answer right there.

Trust only works locally throughout family and closely knit communities, but globally trust is like fiat currency, on a large global scale it is completely worthless on its own, without any higher form of enforcement through violent means to defend and enforce the relationship where the winner dictates the conditions and everyone else has to follow.

Countries don't trust the US government, but they trust and use the USD because they trust the US will do everything militarily to protect it. That's as far as trust goes.

That's only been observed for small, close knit communities (regardless of race etc before the pitchfork activists come out). You're never ever getting that for the whole world. Some things (not all) are just a conflict of interest. There's no solution except one with a winner and a loser.

That does not work with ideologies that see war as natural or good, as in the example you replied to

it's naive to think that the wars of the 20th century were caused by lack of trust, or the 21st

You know, you increase trust also by arresting actual criminals

So when the police is happy to fine you for any technicality while people are free to do drugs on the streets (due to bad policy) this brings trust down - like in SF