1. Rejected from working in a gamedev in Europe because I am not EU Citizen.
2. Lots of companies on USA have to follow some crazy tax rules or general regulations that make them not allowed to hire foreigners, don't even need to be military stuff. Noticed some companies won't even hire out of state.
3. Military, healthcare and many other industries for obvious reasons don't accept foreigners.
4. Several companies have some for reason or another have all employees working on the same time, meaning they refrain from hiring outside their timezones (thus no California companies for me, and no Europeans either)
5. A bunch of times had problems because mismatch of required education and how education work in different countries.