facet_order_barplot

require(dplyr)
require(ggplot2)
# make sure that purrr package is installed to use purrr::set_names

# aggregate data
df = mpg %>%
    group_by(year, manufacturer) %>%
    summarize(mixmpg = mean(cty + hwy))  %>%
    # create dummy var which reflects order when sorted alphabetically
    mutate(ord =sprintf("%02i", as.integer(rank(mixmpg))) )
    
# `ord` is plotted on x-axis instead of `manufacturer`
ggplot(df, aes(x = ord, y = mixmpg)) +
  # geom_col() is replacement for geom_bar(stat = "identity")
  geom_col() +
  # independent x-axis scale in each facet, 
  # drop absent factor levels (actually not required here)
  facet_wrap(~ year, scales = "free_x", drop = TRUE) +
  # use named character vector to replace x-axis labels
  scale_x_discrete(labels =  with(df, as.character(manufacturer)%>% set_names(ord))) + 
  # replace x-axis title
  xlab(NULL) +
  # rotate x-axis labels
  theme(axis.text.x = element_text(angle = 90, hjust=1, vjust=.5))

Forgive me my ignorance, but what is this dataset that you used here? I would like to replicate this example.

Forgive my ignorance of not properly including required libraries in the first place. :-) I've updated the example to be more self-contained. mpg is loaded along with ggplot2 package, see https://ggplot2.tidyverse.org/reference/mpg.html#ref-usage