Johnson demands Zelenskyy fire Ukraine’s ambassador to US amid fallout from Pennsylvania trip

It appears you're referring to a current event or news story. As an AI, I don't have real-time access to breaking news. However, I can provide some general information based on the details you've given. If a figure like Mr. Johnson is demanding that Ukraine’s President Zelenskyy fire the Ukrainian ambassador to the US, it's likely due to some kind of political disagreement or controversy. An ambassador serves as a representative of their country in a foreign nation, so any perceived misstep has potential diplomatic consequences. The fallout from a trip to Pennsylvania could either be due to the events during the trip itself, or could be a coincidental event that's impacting the relationship between the countries involved. For the most detailed and recent information, please check the latest updates from a reliable news source.