library(rnaturalearth)
library(sf)
library(dplyr)
world <- ne_countries(returnclass = "sf")

# filter the world sf object down to canada
canada <- filter(world, name == "Canada")
# coerce cities lat/long data to an official sf object
cities <- st_as_sf(
  maps::canada.cities,
  coords = c("long", "lat"),
  crs = 4326
)
# A PROJ4 projection designed for Canada
# http://spatialreference.org/ref/sr-org/7/
# http://spatialreference.org/ref/sr-org/7/proj4/
moll_proj <- "+proj=moll +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84
+units=m +no_defs"
# perform the projections
canada <- st_transform(canada, moll_proj)
cities <- st_transform(cities, moll_proj)
# plot with geom_sf()
p <- ggplot() +
  geom_sf(data = canada) +
  geom_sf(data = cities, aes(size = pop), color = "red", alpha = 0.3)
ggplotly(p)