(US) Why is the presidential election treated so importantly if the president has the least power out of all positions in government?

Oh, no, he has the most power of any individual in the government - it's just nowhere near as much power as many people seem to think. A lot of his power is negative (the veto) and most of the rest is in controlling who runs each government department, and how; along with appointing judges: so it's mostly indirect power, but it's still unquestionably powerful.

Because us americans don't actually care about politics. The president is a puppet but we refuse to see beyond the surface

actually, after 9/11 Congress granted the president sweeping powers.. these powers can only be rescinded by the president wich has not yet been done.. making the president more powerful than any other since world War two...
couple this with provisions in the Patriot act and you will see that the president has more authority than ever..

The president doesn't have the LEAST power, just not as much as some people think.

Veto power is the least amount of power? Are you sure about that?