Edit: I found data for more countries, included bulgaria in this edit (a whopping 1200).
Also note that many countries have no purpose built mosques, that is no building that is designated solely for being a mosques. Many have just one or two for their whole Muslim population. Some have no congregation centres for Muslims at all -- for example Slovakia or Croatia (with Hungary heading this way as well).
Kept this to the EU + 2 countries (Switzerland and Norway, who are not members) because there is no actual statistics on this and I had to google everything myself. I also removed countries with less than 100 mosques from the list because they were statistically insignificant. Luxembourg for example has 6, Portugal has 16, Italy has 8 -- by all accounts I could find.
Mosques in Xinjiang: 24'300 in 2013, which is still an accurate number in 2021 according to the CPC. https://www.statista.com/statistics/1085676/china-number-of-mosques-in-xinjiang/
Mosques in Europe:
- 1500 in the UK https://www.bbc.com/news/uk-35514840
- 2500 in Germany https://www.dw.com/en/mosques-in-germany-statistics-hard-to-come-by/a-45806004
- 2200 in France https://www.france24.com/en/20150405-france-double-number-mosques-islam
- 1000 in Spain https://traveltriangle.com/blog/spanish-mosques/ (sorry for this link, it was impossible to find anything else. Their number is in the Q&A section at the bottom of the page)
- 100 in Switzerland https://www.swissinfo.ch/eng/mosques-in-switzerland/73624
- 380 in Belgium https://www.pbs.org/wgbh/pages/frontline/shows/front/map/be.html (dated around 2006 though)
- 600 in Austria https://www.washingtonpost.com/world/2021/05/29/austria-islam-map/ (and the source is very apropos lol)
- 170 in Denmark https://www.aa.com.tr/en/europe/mosques-in-denmark-increase-by-48-pct-over-last-decade/1013276
- no data for Norway
- around 175 congregations in Sweden. I couldn't find data for mosques specifically, but I found this https://archive.ph/wip/PZNxB
- 453 in the Netherlands in 2003, doesn't seem this number has changed much https://ec.europa.eu/migrant-integration/librarydoc/the-position-of-muslims-in-the-netherlands-facts-and-figures (see attached pdf)
- 1200 in Bulgaria https://www.novinite.com/articles/143628/Bulgaria+1st+in+Europe+by+Mosques+Per+Capita
Total number of mosques in Europe: around 10378 (I rounded up the statistically omitted data to 100 for this number)
We could also compare the number of worshippers in both places but I spent enough time on the numbers already so this will be very quick. There are 12 million Uyghurs in Xinjiang and I'll assume they're all Muslim. Meanwhile there are 25 million Muslims in the EU (https://www.bbvaopenmind.com/en/articles/muslims-in-europe-the-construction-of-a-problem/).
This means there are 0.41 mosques per 1000 Muslims in the EU, whereas there are 2 mosques per 1000 Muslims in Xinjiang alone, not even in the whole of China!
The worst part is, many of these countries that condemn China don't have a single mosque. This is a map of the countries that signed either of the two letters at the UN, the first condemned China and the second praised it.
Iceland and the Baltic countries condemned China, yet have no purpose-built mosque in their country. Switzerland signed the first letter as well, has around 100 mosques, banned the construction of minarets prior to 2010 (despite the call to prayer already being illegal), and recently banned wearing any kind of veil or head covering in public under the guise of not letting poor Muslim women be forced to wear this very oppressive clothing.
Sweden, as you can see from the post above, has its own problems to sort out: out of 175 Muslim congregations polled, more than half said they had experience one or more attacks against their place of worship. These are very worrying numbers. I was completely unable to find any data about mosques in Norway, probably they don't even know themselves how many they have... if any. Finland is doing okay, they have a total of 40 but just 2 purpose-built; the others serve as multipurpose facilities. For their population of self-identifying Muslims, that's a ratio of 2 mosques per 1000. But we should have to see what these mosques are, because from what I found they were very small, mostly office buildings.