you should really direct all that drivel to the Amish communities, hutterites, Hasidic Jews, the folks of china town, little Italy etc etc etc.
I have been to such communities in the US, and I can tell you that they not only keep their culture, but they also assimilate into American culture. They do not cut themselves off.
Go to any Chinatown and you will see that almost all of the residents, except for mainly the new arrivals, speak English as well as most Americans. They have created an identity in the American culture.
The Amish speak many different dialects, but they also speak English. They participate in government, they vote, and in times of war they volunteer with the government to help, although they refuse military service based on religious reasons. In regards to Tetsujin's comments the difference between the Amish and Muslims that he is referring to is that the Amish do not look down upon other Americans because of their belief. In fact if they did it would be considered a sin (pride). They certainly do not attempt to impose their lifestyle and beliefs on the rest of the population.
Visit Little Italy in New York sometime. Great food and proud Americans abound.
Again, referring back to what Tetsujin was saying, these groups that you mention differ from the Muslims he was referring to because they do not despise the nation that they now call home. You don't see these groups talking about how they want the government to change to accommodate their lifestyle and culture, nor do you see these groups talking about wanting to leave their home to go somewhere else.
Yet it is not uncommon to see Muslims moving to Western countries, then talking about how they are surrounded by filth, godlessness, depravity, etc. It is not uncommon for Muslims to move to democracies then talk about how bad the democratic system is. You don't see that in Chinatown or Little Italy or even in the Amish communities. These communities respect the system and live within in. They appreciate the freedoms they have, yet at the same time retain the parts of their culture that they want to keep.
The Chinese in Chinatown are not complaining about Democracy. The Amish in Pennsylvania are not saying that the US should be under religious rule. I am new to these forums but I have already seen Muslims speaking of their dislike of democracy, the filth and depravity of the West, and seen them try to convince people that everyone would be better under Sharia law.
These, I believe, are just some of the reason why there is a perception difference between the assimilation of Muslims in the UK and the assimilation of the groups that you mentioned.
Do I think these perceptions are accurate? Most likely not. Unfortunately it is often the squeaky wheel that gets the most grease. In this case it is the loudest complainers that get the most attention for their group.