Fuji,
it should not be forgotten that their systems are light years ahead of ours. If you havent flown there, you will simply not understand how good they are.
I haven't flown in the US, but my understanding is that GA is/was almost part of the essential/practical/useful transport infrastructure, no doubt due to it's size and wilderness expanses. GA has an almost irrelevant practical purpose in the UK, it is 90% sport. As IO540 frequently says, if you need to be somewhere...drive.
The UK will never achieve what the US has. The ATS structure will only become more intolerant of errant pilots and thus more inflexible.
Not sure what you mean by integrated: systems or airspace. My view is that the former means expense that we pay for (no thanks). The latter means joining the gaps between CAS (no thanks). Not sure what other practical and realistic options remain
