Hong Kong, which had almost zero cases throughout the pandemic, is now having a massive explosion of cases.
Mainland China is having the highest caseload it's had since the beginning of the pandemic, and it remains to be seen if their massive just-lock-everything-down-and-test-everyone approach will still work on Omicron. Note that a "massive" outbreak in China is still many fewer cases than a normal day in America, even now. The main consequence of this for China is that their zero-COVID strategy requires shutting down large parts of their country for several weeks, and that will disrupt supply chains globally.
Part of the problem is that in both HK and mainland China, most people got the weak and ineffective Sino vac vaccine (or nothing at all) instead of a good mRNA vaccine. As a result, a big Omicron outbreak is much more consequential for them in terms of loss of life. HK is experiencing that now, and China is working very hard to not get there. China also faces the problem that they have to quarantine anyone coming into the country for weeks to maintain their zero-COVID strategy, and that starts to become a big disadvantage as the rest of the world moves on.
A handful of other countries that initially had very good COVID strategies are also experiencing huge Omicron waves right now, but they fortunately deployed mRNA vaccines a while ago and are doing well (eg South Korea, Japan, New Zealand).