Except for the fact that your history is all wrong, I agree with you.
NASA's problems have been many...but one of the biggest has been that they try to push the envelope too much, and then they don't have the budget to see the project through (anybody remember NASP, or the endless series of redesigns of the space station? What about the never-ending quest for a shuttle successor?). Back in the early days, they had more budget, they took smaller steps, and made more progress...Look at the early X planes, for example. Or look at all the rockets they blew up...er...launched before they developed the Saturn V.
As for the Portuguese...let me refresh your memory...ever heard of a place called Brazil? What language do they speak there? What about Goa and Macao? Not exactly on the back side of Lisbon. And Angola and Mozambique? Portugal did amazingly well, considering it was at best a second rate European power...thanks to the foresight of people like Henry the Navigator.
Columbus was from Genoa...in Italy.
If you want a model for the U.S. from the era of colonial empires, I would suggest Imperial Spain. Richest and most powerful country in the world at that time, with an empire that spanned the globe until it frittered away its vast resources in a never-ending series of wars (and more than a bit of corruption). Sounds kind of familiar, doesn't it?
Chris