@Yaworm
3rd) No Cap is not immune to Magic. No one said that. And if you see my earlier comments, you'll see I stated that Geralt's magical abilities would be tough for Cap to overcome...
However! Most of Geralt's abilities can be and HAS been overcome or bypassed by characters and things less than Captain America.
-Igni? Cap has his Vibranium/Proto-Adamantium shield that has guarded him from fire, explosions, and so much more. With Igni it would be no different. Plus, Cap can dodge the attack...hes dodged and deflected bullets, why couldn't he do so with a fire blast
-Aard? A telekinetic force push. Cap again can block or dodge this, he's done so against far worse.
-Quen? A Magical body shield, that can and has been broken by strong individuals. Why wouldn't Cap be able to do so? Even if he could not break it, Geralts Spell Signs are not unlimited or indefinite...basically it fades, or has a time limit. Geralt would not be able to protect himself with Yrden forever. Which gives Cap a chance at a fatal blow.
-Helitrope? A magical barrier that protects Geralt from harm. Same is the case with Quen. It wont last forever, and it can be overcome.
-Axii? Mind Control & manipulation. Geralt does not have this in this fight. Even if he did, Geralt has never been shown able to mentally control strong willed individuals, in fact he rarely uses this (to my knowledge). Even if he has or was able to...Cap has psionic defenses, and experience fighting off mental attacks. Cap could (not definitely) resist Geralts mental attacks.
-Yrden? Its magical trapping. Geralt does not have this here either. But even if he did, this would most likely prevent Cap from pulling out a victory. However, just like with other signs and magical abilities of Geralt, they can be overcome.
Basically, Cap does not need to have magical immunity to fight Geralt.
Now, how do you think Geralt fairs in Round 2, where he can't use any of his magical abilities?