U.S Agent on his own is very basic ally. Retaliate, 5 hit points, 1 ATK, 1THW. If FFG included him in core set, one no one see the difference. But this card got one problem: needs building. Maybe for the retaliate (Ready for Action is obvious choice), maybe adding more health (Reinforced Suit) or maybe to boost stats (example: Inspired, Power Gloves). Unfortunate there is a answer to all of this: every one of this three instances are more worth it to build with another allies.

Of course if you got the lucky, U.S. Agent can blocked 2 times (plus remove tough from the enemy) and got the value. But in 2025 where we have 10 waves of cards (and more to come) that beside thematical decks (or having many decks at one time) John Walker is not the sexiest choice.

Rating (A-C) B- Can be quite good, but need time and there is many better choices for voltron