Guerra was born into a motorsport family; his father, Benito Guerra Sr., was a vintage racing driver known for competing in La Carrera Panamericana and serving as a notary public in Mexico City. This upbringing fostered an early passion for competition that would eventually lead Benito Jr. toward a professional career in rallying.
Guerra made his World Rally Championship debut at his home event, Rally Mexico, in 2006, finishing 26th overall. Progress was gradual in the following seasons — he retired from both Rally Mexico and Rally Argentina in 2007 with mechanical failures, but returned to form in 2008 by finishing 14th on Rally México and winning the Group N category. His development continued at the national level: in 2009 he won the Spanish Production title, and in 2010 he claimed the Spanish gravel title outright. At that year's Rally México he finished 15th overall and fourth in PWRC.
Guerra opened 2011 with an 11th-place overall finish at Rally Mexico before committing to a full PWRC programme. He collected consistent points across the season — fourth in Portugal, fourth in Australia, and third in Spain — ending the year sixth in the PWRC standings with 47 WRC points.
The 2012 season was Guerra's breakthrough. He and Rozada took outright PWRC victories at Rally México, Rally Argentina, and Rally España, and added a second place in Germany. Their final tally of 109 points comfortably defeated the Argentinian pairing of Marcos Ligato and Rubén García, who scored 88 points. The title made Guerra the first Mexican rally driver to win a World Championship.
That December, Guerra was invited to the 25th edition of the Race of Champions, held in Bangkok. Competing as part of Team Americas alongside 2012 IndyCar champion Ryan Hunter-Reay, he faced opponents including Michael Schumacher, Sebastian Vettel, and Sébastien Ogier. In the Nations Cup he defeated Jorge Lorenzo and Ogier but was eliminated by Andy Priaulx following a penalty; Team Americas exited in the first round after Hunter-Reay's results were insufficient. In the Champion of Champions event, Guerra was also eliminated in the first round. The overall ROC 2012 winner was Formula 1 driver Romain Grosjean.
Sponsorship difficulties prevented Guerra from contesting the Monaco and Sweden rounds in 2013. When he did return — at Rally México with a Citroën Racing privateer entry alongside Rozada — he delivered an impressive debut in the outright WRC category, finishing eighth overall and earning his first WRC championship points. The gap to winner Sébastien Ogier was 12 minutes 49.8 seconds.
Guerra returned to the Race of Champions in 2019, at the 29th edition held at Foro Sol in Mexico City. He advanced through the competition by defeating Sebastian Vettel, Pierre Gasly, Daniel Suárez, and Esteban Gutiérrez before facing French driver Loïc Duval — winner of the 2013 24 Hours of Le Mans and 2013 FIA World Endurance Championship — in the final, which Guerra won.
Guerra's 2012 PWRC title placed him in a very short list of Mexican motorsport world champions. His achievement is viewed as a landmark moment for Mexican rally driving, opening a path for future competitors from the country on the world stage. His victory at the 2019 Race of Champions on home soil, against a field of established Formula 1 and endurance stars, underscored his longevity and skill in cross-discipline competition.