[wahern]

> Also, the UK wasn't a democracy in any meaningful sense in 1776

And the U.S. was? Much like the UK, the franchise was reserved to a subset of land freeholders. Only about 10-20% of the US population was eligible to vote. (http://www.crf-usa.org/bill-of-rights-in-action/bria-8-1-b-w...)

The UK did and still does have a written constitution, it's just not entirely written, and what's written is spread across multiple documents--the Magna Carta being one of the obvious ones. The US is not that different. Much of the US Constitution, especially the Bill of Rights, was copied verbatim from the written parts of the English constitution. And even conservative American jurists who reject Substantive Due Process regularly recognize unwritten constitutional rules and norms, especially those deriving from English constitutional norms.

Aside from federalism (where states maintained some sovereignty), the most fundamental constitutional differences between the US and the UK relate to judicial review and parliamentary supremacy. But it didn't become clear until 1803 in Marbury v. Madison that the US would follow a different path. If Congress was the final arbiter of legislative constitutionality (as many believed in 1789, and some conservatives argue to this day), there would be little if any functional difference between the US and UK constitutional systems. Indeed, now that US Senators are directly elected, but for Marbury v Madison even federalism would be little different than UK's so-called devolution. Japan nominally has judicial review, but their supreme court has zero inclination to strike down legislation so in practice the Japanese legislature has similar constitutional powers as the UK parliament.