Yes, it is super competitive. A few things to know:
+ It is tougher to get through MBB as a Business Analyst stratight out of undergrad than as an Associate post MBA. For instance, McKinsey has a pyramid structure where their incoming class each year has 30-40% fewer BAs compared to Associates
+ Your school matters. Recruiting teams have a set target from each core school. A top MBA core school like HBS/Kellogg/Booth will have more people accepted than other schools
+ The office does matter, but not to such a great extend. It's true that the San Francisco office would have more demand than let's say a Cleveland office, but the number of Associates San Francisco is looking for will also be significantly higher. Sometimes smaller offices (<50 people) like Cleveland are looking for just 1-2 people to join each year. So, in the big picture it really doesen't matter
Having said that, these are things you should not worry about. Just focus on crushing the interviews. If you're above the bar, these firms will not let you go anywhere!