If USA were to adopt Spanish as the national language instead of English, will Spanish become Lingua Franca of the world?

If, through natural population changes and cultural shifts, If Spanish becomes more predominate language in the United States, English would still be the Lingua Franca of the world. Even with Spanish predominance, English would be a necessary second language, much like it is in Quebec. The fact that the first language of most Americans is Spanish (thus it is a "national language") would likely to do little to diminish English as being the most common language known. It would just be known as a second language instead of a first. Much as it is in Holland or Switzerland, where nearly everyone speaks it. Lingua Franca is a tool for international communication between ALL countries. Not just between the biggest player and all other countries. For further consideration, I offer this question about the next foreseeable Lingua Franca:

Spanish becoming the dominant language of the US would definitely increase its global position. However, it's limited by the fact that it is only prominent in the Americas and Spain. So it would solidify Spanish's position as the primary language of the Americas, but English would remain the lingua franca of Europe, Africa, and South Asia.

Why would the United States switch from English to Spanish, though? If it was because Spanish had become the main language of Americans, somehow, then maybe the world would follow suit. If the US was the leading state of a Spanish-speaking community of a half-billion people, then maybe the world would also adopt Spanish. Especially if Spanish was adopted as an additional language to English--really, the only plausible option at this interval given the rates of language shift from Spanish to English by Hispanic citizens of the United States--English would still prevail. Besides being the main language of a quarter-billion or so Americans, English would still be very widely spoken by more than a billion non-Americans (Europe, Africa, South Asia, et cetera).

Languages are not interchangeable. They are the backbone of culture. There are thoughts that are easier to think in one language than another. And nations that speak the same language (or closely related languages) are tied together culturally. If the USA suddenly were to replace English with Spanish as the commonly used language, the consequences would be most drastic for the nation itself. It would become unlinked from a group of prosperous nations and become culturally linked with a group of significantly less prosperous nations. This would influence trade, education, and foreign policy, at the very least. I would bet good money that the result would be a drop in US wealth and influence, permanently. Just how hard it would be hit is however hard to predict. If the USA lost its economic and military hegemony (and this is the way things are moving already, so it could easily happen) then no, Spanish would probably not take on the role that English has today. But English might lose it, at least over time. We might enter an era of greater fragmentation, with at least English, Spanish, and Chinese languages living their own lives side by side each with 1 - 2 billion users including fluent second language users.

The USA don’t determine what happens elsewhere. English is not an american property, it was firstly from England and it also expanded from colonies etc. It’s easy to learn, more than spanish and it’s practical. In the every day life, when we encounter foreigners, we speak English and most of the time they’re not americans.Assuming it would never happen, I don’t think we can mesure the consequences if it would have but I don’t believe a language would change that many things. It would take a lot of time to pass from English to Spanish and we wouldn’t spot the changes.P.S: it’s highly unlikely Spanish would become official unless the USA acknoledge it as actually being part of their countries culture as well. With Trump, we’re far from that!

No.It is wrong to think that English today is lingua franca of the world mostly because of the United States. That’s a misconception.The fact that English is today the lingua franca of the world also has a lot to do with Asian countries like India, Singapore, Malaysia and African countries (owing to colonialism by the British). If America chooses Spanish as it’s national language, Spanish would definitely grow in popularity, but it wouldn’t outgrow English.English has already made it’s mark in several nations and people would learn it anyway (even in the United States). Thus, learning Spanish wouldn’t become absolutely rudimentary for a huge population in the world. I don’t see businesses suddenly doing their operations in Spanish. English would still remain the lingua franca of the world.

Yes, If USA did adopt back to its foundation Spanish rather than English, Spanish would have been the modern Lingua Franca.

I think so. If Spanish was the most important language in the USA, Latin American countries, Spain, France, Brazil an Italy will use Spanish language immediately as lingua franca.English would be used by United Kingdom, India, Canada or Germany.Other countries like China,, Korea or Japan will study which one to use. Probably both.It is not clear. Both languages would be very important, but perhaps Spanish was the winner.