I have a VERY good ear for accents; especially ones from all of the 5 NYC boroughs, and can pick the sounds apart, in other's speech.
I have NEVER heard Trump's accent, before he threw in his hat, for the primary, and because it was SO strange to me, have paid a great deal of attention to it.
My grandmother was fascinated by NYC accents and I got my interest in them and learned much from her! And as I grew older, also did my own research into accents.
My accent would completely confuse you! LOL
I'm very surprised that you hadn't heard Trump's accent before, being so familiar with NYC and environs. It's not as if he hasn't been a highly public figure for more than three decades.
How did he evade your detection?