That college you are trying to apply to probably is a private college who purpose is among others, to make money. It would be beneficial for them to make go go through some course first before you can enroll in their degree program. Basically, they have the power over admission, so you can try arguing with them that your High School diploma should allow you entry straight into their degree program. Or just accept that it's equivalent to SPM. The final year in Malaysia is called Form 6. That is the year before you enter college for a degree program. By the way, did you really spend the last 10 years studying in the US? I've never heard anyone say chopped there, they always say stamped.

Btw, the Malaysia government has decided that US High School Diploma is equivalent to SPM. I am looking at the document right now. So I find it strange that the people at the ministry didn't know what it is and decided it's equivalent to O-Levels, which isn't even a Malaysian education qualification.