if arguments is equal to this string, define a variable like this string

I am doing some bash script and now I got one variable call source and one array called samples, like this:

source="country"
samples=(US Canada Mexico...)

as I want to expand the number of sources (and each source has its own samples) I tried to add some arguments to do this. I tried this:

source=""
samples=("")
if [ $1="country" ]; then
   source="country"
   samples="US Canada Mexico..."
else
   echo "try again"
fi

but when I ran my script source countries.sh country it didn’t work.
What am I doing wrong?