In 1999, the US quietly sent a signal. Its U17s, led by Landon Donovan, DaMarcus Beasley, Tim Howard, and Kyle Beckerman, went to New Zealand and reached the semis of the Youth World Cup. Donovan was named the best player in the tournament.

In 2000, the US sent even a stronger signal. The 99 U17 squad, plus some kids named John O'Brien and Josh Wolff, with some veteran help from McBride, Hejduk, and Friedel, reached the semis again. This time, in the Olympics.

In 2001, the "dos a cero" era was born. On February 28th, those kids, plus another young hotshot named Clint Mathis, turned the game around and beat Mexico in WCQ 2-0.

For the next 12 years, those US kids dominated Mexico. In 06 and 10, the US qualified first out of CONCACAF. In 13, San Zusi rescued Mexico. The US won more Gold Cups (4-3), had a better head to head record (10-4-6), and beat them at the WC itself.

In 05, Mexico started to send signals of its own. Led by Vela, Dos Santos, and Moreno, they won the U17 WC. In 2011, they won the U17 WC again (it was in Mexico, but still). In 12, Mexico won the Gold Medal in the 2012 Olympics.

Meanwhile, the US entered the "lost generation" era. The list of US failures is pretty depressing:
- 2012 Olympics DNQ
- 2013 U17 WC DNQ
- 2015 U20 WC DNQ
- 2016 Olympics DNQ

The core of the US team was getting old, and the next classes failed to produce quality replacements. Mexico, OTOH, was emerging. The decline in results was predictable:
- Gold Cups: MEX 2, US 1
- 2018 WCQ: MEX 1st, US 5th
- Head to Head: 2W, 4L, 2D

So the point. I don't think youth results are perfectly predictive, but a couple really good youth classes can change senior team results for years. That seems to be especially true when you have multiple classes in a row of high-ceiling players.

So how have things looked in recent youth results? Going back the past 3 years (arbitrary cutoff):

2017 U17 WC:
- MX: 3rd in group, lost to Iran in QF
- US: 3rd in group, lost in England (eventual winners) in QF

2019 U17 WC:
- MX: 3rd in group, reached final
- US: Last in group

2017 U20 WC:
- MX: 2nd in group, lost to England in QF
- US: 1st in group, lost to Venezuela in QF

2019 U20 WC:
- MX: Last in group
- US: 2nd in group, lost to Ecuador in QF

The US seems to have developed players reaching a higher level of club play (so far), but I would bet the next few years are going to be more of a dog fight in one of the world's best rivalries.

BTW, this thread was me checking my own opinions as much as anything, and I'm not sure it's worth reading. Will probably go into the dumpster soon.