Honestly? I think the entire world would know about a war fleet landing in America. The Empire of America likely has noticed. I don't recall if they have satellites, but this is the late 21st century... You know, where you cant sneak war fleets around the coast line of a foreign country, especially one which is likely watching for invasion anyway... Any country which isn't now would be insane 
The ships entering their water would be enough to make the Commonwealths demands relevant anyway
Of course, I am assuming you launched from ships, if not you skipped over half his empire. He would have detected your planes coming in, and if they flew from Antarctic they likely passed near my lands and just beyond that is the EoA so its not had to call it an invasion because you flew military planes into his air space. 

To conclude: Thanks to your planes, it would take a miracle for the imperials NOT to have found that base now, and another miracle for the Empires neighbours not to have noticed you flew planes into his country. And that's nit even considering satellites, which make both of those even more likely.