Q:

Ploting a Buffer Around a Point on a Map - R SF

I've been trying to plot a buffer around a point on a map but when I do the buffer doesn't appear in the right place like this.
Faulty R Map
The correct location is in California.
Here's my code:
library(tigris)
library(sf)
library(tidyverse)

projection <- 102003

options(tigris_use_cache =  TRUE)
county_polys <- counties(class = 'sf') %>%
  filter(STATEFP %in% c('06','41','53','04','16','32','49')) %>%
  st_transform(projection)

  centroids <- county_polys %>%
  as_tibble %>% select(INTPTLON,INTPTLAT) %>%
  mutate(
    INTPTLON = as.double(INTPTLON),
    INTPTLAT = as.double(INTPTLAT)) %>%
  st_as_sf(coords = c('INTPTLON','INTPTLAT'), crs = projection)

 pt <- centroids[2,] 
 pt_buffer <- st_buffer(pt,150000) 

 ggplot() + geom_sf(data = county_polys) + geom_sf(data = pt_buffer,color = 'red')

A:

We can use the st_centroid function to get the centroid to avoid errors. There is no need to convert the sf object to other classes.
# This is the only thing I changed from your original code
# Get the centroid by st_centroid
centroids <- county_polys %>% st_centroid()

pt <- centroids[2,] 
pt_buffer <- st_buffer(pt,150000) 

ggplot() + geom_sf(data = county_polys) + geom_sf(data = pt_buffer,color = 'red')

