It seems we're at a crux in history and the world can go one of two ways, depending on what America does:

1. The US becomes a half-Western half-Asian nation and remains No.1, with Europe/Russia and China/Asia a distant 2nd equal.

2. The US slowly federates with Europe (and maybe also Russia), retaining its primarily Western culture. The Europe/USA bloc and China each have equal influence in the world.

(1) The first would happen through mass immigration...

> Nearly half of all graduate students in the sciences in the U.S. are now foreigners, most of whom will be heading home, not staying here as once would have happened

That's mainly because of the US government rules. Australia has more relaxed rules and thus the international students stay. The US can change the rules anytime it's expedient. The lessons from Canada, Australia, and NZ is that eventually the people vote for whatever makes the house prices and rents go back up. International students and immigrants make incomes from residential property go up, both rent income and resale gains. Asians, mainly NE Asians, have the most money, and many want to live in a Western country if they can. If their children speak American English, then they're Americans.

The USA, like Canada, Australia and South America, is based on immigration. If the US let in millions of educated and/or wealthy Chinese, they would come and stay _for the same reasons_ Europeans came to America a century and more ago. Ditto Indians, Koreans, Japanese, Thais. The individuality of their home countries won't change, even in nominally "democratic" countries like Japan, which is just a veneer over a very entrenched hierarchical society many young people would escape if they could.

The US has a good food and water supply and can easily accept many millions more immigrants. The Mississippi basin is the largest food growing area on the planet, which is how it rose to global power in the first place. Other food supplies, e.g. Yangtze and Ganges, feed many times the 300 million the Mississippi feeds.

If half of America's citizens in 2030 weren't born there, America would still be "No.1".

(2) The alternative is an international federation...

The US is a federation. Other Western countries became federations because of the US example, e.g. Switzerland in 1860, Canada in 1880's, Australia in 1901, Germany in 1948. With the EU, countries with different languages have half-formed a federation. France and Germany may soon coordinate their fiscal and tax policies, strengthening the federation.

As the US declines, it can surrender aspects of its sovereignty to a similar international federation made up of other Western countries with similar values. Perhaps it'll form a union with other majority English speaking countries UK, Canada, Australia, and NZ. It's already united to them under the UKUSA security and ABCA defense treaties. Perhaps it'll surrender sovereignty to an enhanced NAFTA, sharing a common border with Canada and/or Mexico. 130 million Mexicans suddenly entering the US labor market under a shared labor market would boost the economy massively. Or maybe the US and EU will form a progressively closer union over the next 50 years. If Russia joins, that's 1 billion people, centered around the Arctic, with far more land and resources than China, and especially India.

But the U.S. would be the biggest member of whatever bloc it joins, whether Nafta, European countries, English-speaking countries, or even eventually all three. It would therefore would have the most influence. Because Brazil is the largest country in South America, it can indirectly control the entire continent because the remaining people there who speak the other language are divided into various "countries". In the same way the US could have the most influence in any union it forms.

If "America" is defined as the constitution, the Immigration alternative preserves America better. If "America" is defined as a Western culture, the "Federation" alternative preserves America better. Perhaps both options (or neither option) will play out for a while, but sooner or later one of them will tip the future direction of America's future role in the world, and no-one will know until much later. But there are other options not mention in the article...

The US President and/or Congress could declare the homeland territory to be a "battleground", thus enabling the military to "buy" (annex?) large areas of US territory for military purposes, transfering their jurisdiction away from the Supreme Court. Perhaps half of US territory could become a live-in "military base". Freed from the restrictions of democracy and free speech, the military could set up commercial/industrial zones with controls similar to China's, thus competing on a more equal footing with China.