In relative terms, California is more akin to Scotland than England – a sizeable minority rather than an overwhelming majority. Indeed, looking at the US rather makes the point about why an English Parliament is a bad idea and “patchworking” England is a good idea. Even the smallest US state has huge powers of autonomy and yet in many ways the US is culturally more homogenous than the UK. You can have regional government AND retain an English, even British, identity.
On the other hand, the US does have significant faultlines, mainly between North and South, Bible Belt and Metropolitan Coast. Would those factions tolerate a single state dominating the US? As it is, there are growing tensions that may yet turn out to cause a major crisis. We almost certainly DON’T want a system with such a huge difference in size between the largest state (California, 350m) and the smallest (Wyoming, 500,000) – in the Senate both these states have equal representation, creating an inbuilt Republican bias.