Heroism: Captain America

Introduction

He also has been known to suffer from the
serious condition known as "Liefieldism".

Captain America is one of the most iconic superheroes around, dating all the way back to the 1940s.  Created by Joe Simon and Jack Kirby, his origin in World War II has remained relatively unchanged throughout the years as Steve Rogers, scrawny boy with heart who undergoes a fantastic transformation because of a Super Soldier Serum that grants him the near supernatural ability to not look like a complete doofus with wings on his head like little elf ears, and silly boots.

His intentionally patriotic themes make him fairly polarizing:  Many people misunderstand the character as a jingoist symbol of American superiority, but that fails to address his modern incarnation as more of a fish out of water idealist with a strong individualism streak that often puts him at odds with the government he appears to be a literal representation of.

If you're looking for some good Captain America reading, I heartily recommend both Marvel 1602 (no seriously he's in it), as well as the Death of Captain America if you want something new.  Although it does feature his "Death", it also is a great look at how the character is portrayed and impacts the universe around him.  I'd also suggest his 1970s run which features a very interesting political climate (Watergate, and the Vietnam War both put significant strains on the character).

In Marvel Avenger's Alliance he's largely based on the Marvel cinematic universe take on Captain America, which is basically fairly close to his main comic book incarnation, although he doesn't appear as at-odds with his government as Steve often is.  Carrying his trademark shield, he's an excellent character for protecting your team, and in his World War II costume is one of the stronger Bruisers or Tacticians around.

He's also a valuable buy:  He unlocks a premium mission in Season 1, Chapter 11, and is the team up in Season 1, Chapter 12, Mission 2 which is still the best (or one of the best, pending season 2 analysis) place to farm CP once you're in your mid 100s.  He's also an excellent protector, although it's strongly advised to pick up his WW2 costume (in Bruiser or Tactician flavor depending on if you expect more blasters or scrappers).  I'd suggest Bruiser just because it's vastly better for 1-12-2.

PVP Strategy:  Using Captain America

On Attack

Captain America is great for protecting your squishy
damage dealers like Iron Patriot.  MURRICA!

Cap is an aggressive protector:  He triggers tons of counterattacks, so you want to have him set up to maximize your utility from that with some attack ISO to make sure he hits hard.  He's vulnerable to being debuff stripped however, so beware.  He also provides an excellent buff to the party just for being around, but his protect sequence often leads to his main impact being in the first round or two of a fight.

His attack sequence is tragically a little boring:  Leading Strike, then just use whatever you feel is right for the situation, and refresh Shield Guard once his alternate costume's buff wears off.  This is one of Captain America's main weaknesses as far as a character you're interested in using:  He's a bit of a one-note character.  The note is a good one, sure, but it's still fairly mundane.  This might be because he hasn't had much of an update since they first implemented him, and many of them aren't as complex as the currently available heroes.

He's still a very powerful protector however:  His ability to protect from AOE attacks right at the start of the fight takes away several one hit KO strategies by himself, and he can ruin teams that rely heavily on that.

On Defense

Cap's AI is pretty good!  He will always recharge Shield Guard if it goes down, and like many straightforward heroes he doesn't need much to be good in the hands of the computer.  Correctly ISOing him and providing him with a good backup team is very important, though, as he often goes down fairly quickly to dedicated fire.

PVP Strategy: Facing Captain America

As mentioned earlier, his protect is a buff and can be removed, which renders his utility fairly low if you have a way to give him Cornered, Soulfire him, or Scroll it away.  If not, you're in for a bit of a slog.  Bleeds are also particularly good here, as he makes many attacks if you proc them, which can result in him bleeding out if you really have no way to deal with the protect.

Additionally, his damage is fairly low so against low damage pairings you can often take the time to defensively set up, and wait for his protect to fall off naturally.