The US shelved most of their tactical nuclear weapons in the early 1990's . The US only deploys 2 tactical nuclear weapons types today the Tomahawk TLAM-N SLCM (BGM-109A) which has a yield of 200 kilotons and B61 Mod-3,-4,-10 gravity bomb
(tactical) which has a yeild from .3 to 170 kilotons. Considering that these are gravity bombs they will most probably not be used. Therefore we are taking about a 200 kiloton warhead. All this info is from here: [link|http://www.cdi.org/issues/nukef|http://www.cdi.org/issues/nukef]&f/database/usnukes.html#nonstrat
here is 1 quote:
"The U.S. once deployed the entire panoply of tactical nuclear weapons
(from nuclear artillery and demolition mines to short-range rockets and
even air-to-air missiles). However, nearly all have been removed and are
slated for destruction, largely as a result of President Bush's unilateral
initiative of September 27, 1991. Indeed, the only operational non-strategic
forces are currently the B61 tactical bombs, largely allocated for use
in Europe (and perhaps the TLAM-N SLCMs, though these could arguably be
considered strategic, and are in storage in any case.)"