The best chance for a med school admission is usually in the applicant’s home state. This is especially true if the state’s public med school(s) has/have highly protected admissions. (i.e. strongly favor in-state applicants)
Generally speaking, attending an OOS undergrad has little effect on in-state admission for a state med school. Often state med schools use the location of a student’s high school of record to determine if they will get any in-state preference. However, some (many?) states expect applicants to have demonstrated an affiliation to their home state through recent community service and/or to have demonstrated an intent to remain in-state to practice after med school graduation and residency.
Since public med schools have as their mission to provide physicians to serve in the state, A student from Wisconsin who attends Alabama (to use your example) would not get much–or any-- special consideration from Alabama public med schools–which have strongly protected in-state admissions. The student is still a resident of Wisconsin and would get admission preference in Wisconsin. The only way for the OOS student to gain preference at Alabama med schools would be to remain in Alabama after college graduation, establish residency there, and demonstrate an intent to remain & eventually practice medicine in Alabama.
If you look at AAMC FACTS tables A-1, A-3, A-4, A-5 (see https://www.aamc.org/data/facts/applicantmatriculant/), you can start to get a feel for which state strongly favor the in-staters. Even more detailed data on in-state vs OOS interview & acceptances rates are available in MSAR and USNews. (subscription required)
There are some public med schools that accept very few OOS students: all Texas publics, UC Riverside, New Mexico, North Dakota, East Carolina, Arkansas, LSU, Mississippi, CUNY, Oklahoma, Tennessee, Washington St., UWash (WWAMI residents only), Puerto Rico, MUSC, Alabama, South Alabama, SIU, Indiana. These schools provide great opportunities if you are a state resident, but applying to them as an OOSer may be waste of your application $$. You need to carefully read the admission page for these schools to look at the selection criteria. (For example, both UND SOM and UNM SOM are national magnet programs for Native American students and NA applicants are considered on the same footing as in-state residents.)
OTOH, California public med schools have very little stated preference for in-state residents. (Except for the UC-Riverside program which only considers residents from the Inland Empire area).
And then there is UVermont–which has a strong in-state preference but because the number of in-state applicants is so small 80-85% of each in-coming class is made up of OOSers.
What all of this means–your student needs to do their research when it comes time to apply to med school. Read each school’s admission page carefully to find its admission criteria, state residency preferences, and the school’s mission statement.
Private med schools are a whole 'nother story. Privates generally display no state residency preferences at all.
The knock on CA for undergrad is a volume issue. CA alone produces 10-15% of ALL med school applicants at a national level every year. (>6000 annually) It’s easy for even good applicants to get lost in the crowd during undergrad. Additionally there is huge competition for volunteer positions in hospitals near college campuses, for positions in on-campus research labs, and for top grades at the UCs in the pre-med"weeder" classes.