Yeah, I don't think racial diversity counts for the trust issue. Obviously there are some people that won't trust someone based on their race, but it seems like most groups are willing to accept anyone as long as they follow cultural norms; skin color just seems to be a quick proxy for "they look different, so they're probably culturally different". Just watch the aftermath of a local football team winning a big game. It doesn't matter if you're rich or poor, black or white, everyone in the city celebrates together.
What if your nation had laws that for a century forcibly excluded one race from the dominant culture? The idea that "acting white" is a "get out of racism free" card is a vicious myth.
The US was drastically less racially diverse 50 years ago. It was 90% non hispanic white in 1965 before immigration laws were changed.
I mean, sure, everyone that a given person was likely to see spoke english, ate chicken, and went to some form of Christian church on Sunday. BUT, some of the people were white, some were native american, some were black, down in Texas area you even had hispanics. So the US was pretty diverse. Unless we're not counting racial diversity?