Ich zitiere mal die usembassy Seite:
J Visum:
"The "J" visa is for educational and cultural exchange programs designated by the U.S. Department of State, Exchange Visitor Program and Designation Staff, "
"The "J" exchange visitor program is designed to promote the interchange of persons, knowledge, and skills in the fields of education, arts, and sciences. Participants include students at all academic levels; trainees obtaining on-the-job training with firms, institutions, and agencies; teachers of primary, secondary, and specialized schools; professors coming to teach or do research at institutions of higher learning; research scholars; professional trainees in the medical and allied fields; and international visitors coming for the purpose of travel, observation, consultation, research, training, sharing, or demonstrating specialized knowledge or skills, or participating in organized people-to-people programs. "
Ich denke nicht, dass du im Rahmen eines solchen Austauschprogramms dein Pflegepraktikum machst oder?
B-Visum ist geeignet für volunteers (und ich denke darunter wirst du laufen):
siehe Seite 8 dieses Artikels, dort ist aufgeführt wofür B1 geeignet ist:
http://foia.state.gov/masterdocs/09fam/0941031N.pdf