State Bounced Opened Delivered
FL    2       1      0
NY    0       1      1

State Total
NY    2
FL    3

State Bounced Opened Delivered
FL    66.66   33.33  0
NY    0       50     50

dt1[, percen:=Bounced/dt2$Total]

cbind(State = df1$State,
      df1[, -1, with = FALSE]/df2$Total[match(df1$State, df2$State)]* 100)

#   State  Bounced   Opened  Delivered
#1:    FL  66.667    33.333         0
#2:    NY  0.000     50.000        50

dt1 <- data.table(State=c('FL','NY'), Bounced=c(2,0),
                  Opened=c(1,1), Delivered=c(0,1), key='State')
dt2 <- data.table(State=c('NY','FL'), Total=c(2,3), key='State')

colsToDivide = c('Bounced','Opened','Delivered')

dt1[dt2, (colsToDivide)  := lapply(mget(colsToDivide), function(x) {x/Total} ) ]

   State   Bounced    Opened Delivered
1:    FL 0.6666667 0.3333333       0.0
2:    NY 0.0000000 0.5000000       0.5