Sevilla, Spain is the poster-child of rapidly building out a bike network[0], and with the political will, that could be replicated elsewhere (especially somewhere flat and sunny like LA). Another easy way to improve transit is paint dedicated bus lanes for BRT lines. Not as sexy as dropping a few mil on light rail, but quick, cheap, and rapidly scalable.
[0]: https://usa.streetsblog.org/2018/05/07/six-secrets-from-the-...