As part of the release of Safari 15.5, there seems to be an issue with Safari being able to load embedded content on some websites. One example is the US State Department’s site for reporting a lost or stolen passport:

https://travel.state.gov/content/travel/en/passports/have-passport/lost-stolen.html

This site has embedded content and Safari is very slow to load that site. The behavior seems to be tied to the Hide IP address from trackers setting in Safari’s privacy settings:

With that setting enabled, slow website loading:

With that setting disabled, normal website loading: