I cannot get my coordinates to match up correctly on the background layer. At first, I couldn't even get the QMS Google Satellite (CRS: WGS 84) to show up when combined with my data layer (same CRS). Now I've moved to using Open Street Maps and the background map shows but my coordinates are on the west coast of Africa when they're supposed to be in Los Angeles.
I'm assuming there's some issue with my data or just the projection?
Right-click your Parks layer > Layer CRS > Set Layer CRS... > choose EPSG:4326 > OK. If that doesn't work, proceed the same way for the background layer and set it to EPSG:3857.
You probably either loaded the layer with the wrong CRS definition assigned or afterwards changed (set) the CRS manually (as I described above), but chose the wrong CRS.
Never change the CRS manually (if you're not 100% sure about what and why you do that). CRS of different layers do not have to "match" - you can have several layers in different CRS and even the project CRS can be still another one. QGIS will handle this in the background and place layers correctly (reprojecting "on the fly").
This is a very common problem (many question here on GIS SE). Every layer must be defined in the CRS the coordinates are saved in. In your screenshot, we see LAT/LON, thus probably EPSG:4326. If the layer has assigned another CRS, these values will be interpreted in a wrong way, e.g. as being in meters, not degrees.
It's easy to understand why that must fail: Thus your coordinate values (like 34 degrees north/118 degrees west) will be interpreted as being 34 meters north and 118 meters west of Null Island (intersection of equator with prime meridian). Than explains why it is in the Atlantic.
See here for more details about this: Changing shapefiles from geographic (WGS84) to projected (EPSG:2263) coordinate system using QGIS
