The US has had 50 stars for longer than it has had any other configuration. About time for us share the blessings of liberty with others.
The world economy has grown by 11 percent in the last 3 years, ALL in the US. We have added the equivalent of CHINA to our economy. Certainly Mexico could benefit from good government, and we could establish a American Union capital far away from Washington, DC, say Utah or Nevada. Mexico and Canada are our biggest oil suppliers, and we would benefit from subtantial control over their immigration policy, which now impacts us, but we have no leverage.
So, how would you design a flag for 70 stars/states?
I don't even know who you are.
Back when America was growing rapidly in territory there was a common if not universal assumption that it would include everything to the Pacific and at least into South America, perhaps some of Canada, the western parts. It might still; Destiny is sometimes delayed but never stopped.
LOL! So you think "good government" makes for a good country? Go back to DU where you belong!
Mexico's problem is that it is full of Mexicans. People determine the characteristic of a country, not environment, not constitutions and especially not politicians and bureaucrats. (Liberia's constitution is almost word-for-word the US Constitution.)