I'm going to cut straight to the point: Captain America should be punching vampires in Transylvania in Captain America 3.
My reasons for this are sixfold...
1. It's where he belongs
Captain America just fits doing his fighting in gloomy rural Europe. It's where he first proved himself, it's an environment he knows, and he's been there before.
Imagine the nostalgia of him fighting his way through a place that hasn't changed since WWII. Captain America would literally be in his element.
2. An explanation for Captain America's existence.
Dr Erskine's magical miracle formula for creating super soldiers is something that never quite worked for me. This could work as an origin for the SSS (Super Soldier Serum).
In an era where genetic engineering wasn't even a coined phrase, one man working alone was able to create this flawless chemical concoction, that no one can seem to get right a second time. BS, reasonably sized anachronistic BS.
I suggest that perhaps he didn't create the formula from scratch, and that he instead engineered it from vampire genetics, in order to extract and mass produce the peak attributes of those infected with vampire-ism, but without any of the weaknesses they suffer. Thus, we get the ideal human specimen: Captain America.
This explains the appearance of the serum, and scientifically explains why it does what it does (being essentially an infection of the host).
And would then back up my other reasons listed below...
3. Massive flashback overdose.
Why would they send Cap. there? Because he's been there before. As, it can be assumed, as Stanley Tucci's Dr. Abraham Erskine.
We could open with this story, Dr Erskine escapes Transylvania with a vial of the blood of Dracula himself. Now he needs protection and he has no choice but to return to Germany, the closest nation who are able protect him.
Cap. did a lot of missions in WWII. I doubt all of them were in Norway. So he could have been sent into Transylvania and done a mission or two, who better to send?
4. Vampires (and Transylvania) Don't Age.
If Captain America fought Dracula in the 40's, then it's likely Dracula is still out there. It's also possible that when he went into Transylvania, Cap. could have lost someone to the vampires.
That person would still be alive and in the same state as he was when taken AS A VAMPIRE. What better grudge could there possibly be? What better plot twist that he's still alive? Who could possibly hate Captain America more than that person?
5. Dracula would want Captain America.
Vampire-ism, while granting certain gifts, is predominantly a curse. Captain America's blood could be the cure for that curse. Dracula, if he drinks and assimilates the blood of Captain America, could become all he is and more. Dracula could escape the gloom of Transylvania and take over the entire world. If that's not a villainous plot... then I don't know what is.
This could serve as a conduit to a Blade series. It would establish vampires so well that it would be impossible to explain certain things without them, and that could lead to Blade getting his own movie.
Not only does that fill the need for a more diverse marvel hero lineup, it also provides a gateway to OTHER dark avengers, like Ghost Rider.
So there you go, 6 reasons why Captain America could and should punch Vampires in the teeth!