It's neither nukes, usage of nukes, nor the budget.
The superpower by a common definition is a country that exercises influence over other nations. An empire by the older semantic definition.
What makes USA a superpower?
1. Global economic dominance, US dollars is a de-facto international currency controlled by USA.
2. Geopolitical dominance. USA has major influence with EU, Arab League, South America, Asia, BRIC, AU and international entities like UN, WTO, etc...
3. Military dominance, not through a budget which is just an index of bloat and inefficiency, but through military alliances, oversea military bases and intelligence gathering through allies.
4. Culture export. The whole world knows about America, even when stupid Americans can't place 90% of other countries on a map.
5. Corporate/private entrepreneurship dominance. No country has ever conquered entire Russia, but McDonalds did.
So what is Russia then? It was a contest for superpower title during the cold war, but lost. Still it is a major power.
1. Regional economic dominance. Those neighbour countries don't really stand a chance.
2. Geopolitical influence limited mostly to neigbours. is a leader of some military and political blocks.
3. Military might enough to deter attacks, including from a superpower.
In fact USA demonstrated to be a superpower because it made it's allied countries to intercept a presidential plane.