hey i managed to kill mecha birdo by using an infinite jump cheat with cheat engine
how to do it. first make it to that spot, then get cheat engine atleast 6.2 out and use the process stdrt and set it to 2 bytes
now jump in the game and pause in midair make sure its one jump now type 1 in cheat engine and search. next double jump in the game and pause in midair and type 2 into cheatengine and do next search now jump once then twice and keep going until 5-1 adresses are left if 1 is left then change its value to 9999999 and then the value should change to either 58 and more numbers 53 and more numbers or 51 and more numbers then tick active box unpause game and start double jump in front of mecha birdo to kill him this will count as beating him so you will proceed. if you have more tha one number just do the same thing to the top one and pres active if it doesnt work just try again that way i killed birdo much easier than normally NOTE He still shoots eggs if you break his antenae