Raja is correct. Join us = Come and enjoy our company. Join with us = Come and be like us

It depends on the sentence. They are both used. They have the same meaning, essentially. What is your sentence? JOIN WITH US is "grander" as in: "JOIN WITH US IN THE STRUGGLE!". (strike, revolution, petition) vs. JOIN US FOR DINNER! or Why don't you JOIN US FOR A MOVIE?

It depends on the sentence. They are both used. They have the same meaning, essentially. What is your sentence?...... JOIN WITH US is "grander" as in "JOIN WITH US IN THE STRUGGLE!". vs. JOIN US FOR DINNER!