1. So far I see two debit cards for Americans, bitpay and shift (coinbase.) Are there any that require no verification?
2. Is it possible to use a virtual one and make purchases still in the US?
3. Is it possible to buy preloaded debit card and add to it using bitcoins?
1. There are debit card services with minimum verification like email and mobile number. Almost all providers support USA, check here and find one :
https://bitcointalk.org/index.php?topic=1242788.02. Virtual cards are limited to online usage. Except this there will not be any other differences from plastic cards.
3. Usually preloaded cards are made for one time use. There must be some exceptions too.