The context of that quote is interesting. It's a pep talk to the militia. It could be summarized as "Our country is new and so it doesn't suck yet. Go out there and be honorable."

https://founders.archives.gov/documents/Adams/99-02-02-3102

He didn't intend it as political analysis, but it nonetheless makes a fine warning: "But should the People of America, once become capable of that deep simulation towards one another and towards foreign nations [...] this Country will be the most miserable Habitation in the World."

He's pretty clear that this had already affected every other country, and it seems like he expected us to go that way eventually. I don't think any set of laws will govern a people who would rather defeat their opponents than live together.