What documents does Spain need to apply for a US tourist visa?

I haven't heard that invitations are required for travel.

1, the passport is valid for not less than half a year; The number of visa pages is sufficient (more than 2 blank pages); I'll sign my name on the last page of my passport (be sure to sign it with a black pen).

2. Visa Application Information Form

3.50 mm x50 mm square white background photo 1.

4. Employment certificate (guarantee)

5. Asset certificate: original passbook: transaction details of at least six months; If there is no passbook, you can provide proof of debit card for more than 6 months.

Travel to America, hotel confirmation, air ticket order