From my experience helping a few clients implement Squarespace, it does not work out-of-the-box in mainland China. We discovered it was due to China's internet regulations and Squarespace's reliance on certain cloud services at both the hosting and resource levels. Here is a free tool you can test your one site to confirm: https://www.chinafirewalltest.co/
One of our clients required their Squarespace site for lead generation in China. To help them, we found a service provided by 21YunBox, which acts as a bridge that optimizes Squarespace sites for China's internet. They analyzed the sites to pinpoint slow-loading or blocked resources in China, (images, CSS, JavaScripts, Google Fonts, forms, video files, ect, ect). Then they're solution optimized those resources to ensure they load quickly and are accessible in China, without affecting the performance of our client's regular site. They provided us the optimized site at <SITE-ID-Example>.21cloudbox.com to test its performance from China. We confirmed it worked in China without a VPN, with an average reach time of ~ 100-150 ms compared to 3000 ms - Timeout we previously observed in mainland China. Then we set up geo-IP routing, which automatically directs Chinese visitors to the China-optimized version and global visitors to an international version, all while using the client's normal .COM domain.
Now when our client make any changes to their original Squarspace site, it'll immediately reflect on the optimized China site, including inventory updates. The solution has been in place since mid-January. There were a couple hiccups at first, but they were quickly addressed by the 21YunBox support team. Now our clients are picked up on Baidu (china's Google) and generating high-quality leads from mainland China.
Hope this helps! Good luck 👍