Is an Americano the same as drip coffee? I'm curious about the difference between an Americano (espresso + water) and drip coffee (grounds + water).

Does an Americano taste the same as black drip coffee? Whats the difference in caffeine levels? Process?
Differences


Crema: an espresso has crema whereas drip brew coffee doesn't. The reason for this is that an espresso is pulled under pressure.
Paper filtered: drip brew tends to be filtered by paper of cloth, filtering out oily components. From Comparison of nine common coffee extraction methods: instrumental and sensory analysis (where the French press is similar to espresso in that it isn't paper filtered):


  The most efficient extraction of fatty acids was performed with French Press extraction. Brewing with a paper filter resulted in coffee with the lowest fatty acid content, which is consistent with the findings of Peters.


Of course, this doesn't apply to all drip brews, metal filters don't filter out oily components.


(Possible) similarities


Strength: since an Americano is a diluted  espresso, you can make it the same strength as a drip brew coffee by adding an appropriate amount of water. The opposite isn't true, you cannot make a drip coffee that has espresso-strength. 
Ingredients: both are made using roasted coffee and water only.