No, it isn’t. Listen, the UK has problems with radical Islam, but the UK hasn’t fallen and will not.
The vast majority of UK Muslims aren’t terrorists or nutters or radicals. NOR will they breed us out. After nearly 70 years, they are still 4% of the population, one which is 90% white British. Nor are they even the biggest ethnic group.
Americans really need to stop thinking the UK is three weeks away from death or conquest.
How does that break down into age groups? Today most, if not all, European countries are 90+% "white". But what is the percentage in the, say, 5-20 year-old group? That is wherein the danger lies - the large proportion of older Europeans will be dead and gone in a few years.
Add to that the concentration of muslims in the major urban localities. I think there is ample ground to be afraid for the future of Europe (including the UK) as we know it unless strict immigration measures are taken. First and foremost, expelling all criminal elements. There is an assimilated portion that is welcomed to stay. The rest just need to go.