"There are too many people at the party!"
There are too many cups on the table = 桌子上有太多杯子
There are too many people at the party = 排队里有太多人了 Why the extra 了 for present tense？
了 is used for exclamation here instead of indicating the tense. In Chinese, 了 has a lot of different meanings besides past tense.
That's not quite right, 啦 (la) is mainly used for exclamation, while 了 is used to indicate state change. If le were to be more accurate here, the english would have to be something more like, "(Now) there are too many people at the party!" 排队里有太多人 should be an accepted alternative answer (or the main answer).
In this case 了 used for emphasis together with 太. It has nothing to do with change of state. 太 is rarely used without 了 for emphasis. For example, 太熱了 means "It's too hot", not "It has become too hot".