First thing first. The US does not have an official language in the federal level (although some states do), so saying Spanish is an official language in the US would be a false/misdirecting statement although it is second most spoken/understood after English.

While several languages in Nepal should be given an equal status of a National language, I don't see a serious need of another official language in Nepal where more than 90% (could even be more than 95% if we check with the latest census report) can speak and understand Nepali pretty well. There could be some parts/regions in Himal and Terai where people, for the most part, do NOT understand Nepali and the need of the recognition of their local language as the official language is justified. It could be Maithali, Bhojpuri, Tamang or Gurung or some less spoken language that we may not be aware of to begin with. But as long as those people who use that language can speak/understand Nepali, giving an  official status to their local language is nothing more than succumbing to someone who's  "being demanding for no particular rationale" akin to a kid-crying-for-a-candy IMO.

If you look at India, only 60 odd percent people can understand/speak Hindi and therefore the need of another 22 official languages is justified for such a huge and diverse country.

That said, feel free to argue or bash me to death. I am open to criticism if I am wrong.