That is completely inaccurate. Baltimore and all of Maryland are included in the Mid-Atlantic Region. All 50 states are covered by 8 regions. Local chapters are irrelevant and for that matter, so are the regions when it comes to all-american selections. States and parts of states all have maximum number of all-americans allowed. Coaches submit nominations and all coaches in that state or part of the state vote. District of Columbia (DC, VA, MA) had 21, Maryland- Chesapeake had 10, Maryland- Eastern Shore had 2, Maryland- Howard County had 2, Maryland- Western had 4. Other parts of Virginia had 13. So yes, Baltimore is well represented on the all-american list. You can find the full 2019 list at the US Lacrosse site, players, high school, then 2019 high school girls awards programs.
Sorry, but you made my point for me. The Maryland-Chesapeake AA's are selected by the local Cheseapeake chapter. Every AA selected is from Southern MD. Same for the other Maryland Regions. if you look at the list you referenced on the US lacrosse website you will see that not a single AA is from a Baltimore IAAM School(McDonogh, NDP, St. Paul's, Roland Park, etc). Baltimore shut down their US Lacrosse Chapter and hence no longer have any US Lacrosse AA's.