If I was hiring a full-timer to join our team, and we were an AWS shop, I would be open to hiring someone with a predominantly GCP background as long as they were really good at GCP. Because then of course they can also get good at AWS.
IMHO the recruiting side is over-indexing on very specific technologies rather than personal skills/capabilities (oh, you are a C# expert, great, mind learning Java?). To fight that you could make your resume more buzzword compliant - do a small project in AWS, write a blog post or create a YouTube or TikToc about the differences/similarities, and do a couple of certifications.