Your art looks good. Thanks for sharing.
To answer your questions you placed in the voting poll:
1. Your chances of joining Sega really just depends on how Sonic Mania sells. This is not normal for Sega or any Japan based company to heavily use foreigners in game creation or art. If this game sells well it could open the door for more opportunities.
2. Your best chance to work with Sega is to put together a great portfolio and make good connections in the industry. A lot of art jobs are about who you know from my previous experience before I left the industry. Having work experience that shows you can meet deadlines, work well with people, and are willing to support the art director's vision will help you secure a job too.