Translation:You are angry
Shouldn't "you have been angry" also be accepted ? If not, how would you say "you have been angry" ?
By my opinion given translation is wrong. Should to be as you said - you have been angry.
Yeah, I disagree. Kukasirika is more like "to get/become angry" than simply "to be angry", so Umekasirika is "You have gotten/become angry" (ie. "you are angry" now). It can mean both, but without any context indicating a duration or a time frame, the default interpretation is clearly that you are angry now.
'-me-' is commonly used for states (e.g. anger) that still apply currently. (Something has made you angry and you are still angry.) In English we would use the present tense.