"Need" is a byproduct of two centuries of American imperialism in its treatment of other nations. That has produced enormous hatred and resentment, which the Chinese are using to be "your friend in need" today while economically taking over Latin America and much of Africa.
The image of the "Ugly American" is robust. One of the characteristics is not speaking local languages. In broadcasting, U.S. TV equipment makers almost totally lost the Latin American market because the US companies did not even have manuals in Spanish or Portuguese. The Asian manufacturers did, and had phone support in those languages.
Today, nearly no US gear is sold in radio, either. The only North American company with good sales is Canadian, because those folks are used to multiple languages and have adapted.
Point taken, but my point was that here,
inside the US, one doesn't need to know another language to carry on in commerce, especially since the Immigration Act of 1990 allowed so many people here from other areas of the world -- many of whom knew little English, or Spanish, for that matter, when they first arrived here. I taught Ukrainians and Russians English, and it was a challenge, even though I know a few phrases of those languages.
English is the language that the Ethiopian guy who runs the store I go to, and I, have to communicate with each other. It's the only language the Sri Lankan guy who runs the local car shop and I can use to communicate with each other. The Salvadorans in the restaurant next to my place of work speak Spanish and English. The English is because more than half of their customers are either English-speaking Caucasians, or English speaking Ethiopians, English-speaking Somalis, English speaking Chinese, or English speaking Punjabis. When you have a wide mix of ethnicities in a relatively compact area, English is the only communication tool that can be used. And this reinforces the practice of English being the only language needed in commerce.
In 1950, the English only thing was due to conceit perhaps. In 2021, it's because of all the people who have moved here from other places. In my local school district, 80 languages are spoken by students. The only communication tool they have in common is the English one.
The negative obviously is that Americans going overseas are dependent on people in those countries who speak English, and that lack of foreign language knowledge portrays the 'Ugly American', as you've pointed out.