Mac hardware with firmware before ~2011 is normally a pain in the arse with Linux. Make sure the internal SSD is "blessed" correctly for boot and check dmesg for media/mounting issues with the internal drive.
I would normally agree with you, but on this I run every other Linux distro without many issues (besides Wifi which is in fact a PITA)...
but why cant I even boot from the USB? it simply hangs after selecting it...
Thanks