Kosovo :
Military casualties on the NATO side were remarkably light — the alliance suffered no fatalities as a result of combat operations. The alliance reported the loss of three helicopters, 32 unmanned air vehicles (UAVs) and five aircraft — all of them American, including the first stealth plane (a F-117 Fighter Bomber) shot down by enemy fire. Several of these were lost in accidents and not by enemy action. The Yugoslav armed forces claimed to have shot down seven helicopters, 30 UAVs, 61 planes and 238 cruise missiles. However, these figures were not verified independently and have little support among non-Yugoslav analysts.
Bosnia
FATALITIES: 167 (3 military observers, 159 other military personnel, 1 civilian police, 2 international civilian staff and 2 local staff)
http://www.un.org/Depts/dpko/dpko/co_mission/unprof_p.htmBy April 1995, UNPROFOR forces had suffered 1,382 casualties, 155 of
them fatal. Over 560 of the casualties were war-related, with mines,
shelling, and direct fire each accounting for about one-third of this
number. Thirteen UNHCR staff have been killed, including several
convoy drivers.
http://www.fas.org/man/gao/nsiad-95-148.htmI haven't found any details about the nations involved, but I think the UK/French were the highest because they were the bulk of the orces on the ground
the zero casualties for Americans depend on the fact that no ground troops were involved during the hostilities. The US effort was to 99% air/naval.