I'm from Mexico and planning a trip to Japan, and so me is a few thousand dollars cheaper and way faster to do it from LAX, than from my own country. I do have an American Visa B-2 type (Tourist). What problems could there be regarding my situation? and Are there any extra steps in me taking an international flight within the US as a foreigner? Thank you so much in advance, I really don't want to have an issue and have never done a flight like so.
What problems could there be regarding my situation?
You could be denied entry into the US. Since you already have a B visa, this is probably rather unlikely.
Are there any extra steps in me taking an international flight within the US as a foreigner?
Not really. The airline will report your departure to the US government, so you might have to show your US visa when you leave for Japan, but otherwise the process will be essentially the same as it is for a US citizen.
You want to transit through the USA using a B2 visa. You are unlikely to have any problems.
If you already have a valid visitor (B) visa, you may be able to use it to transit the United States. If you are a citizen of a participating country, you may be able to transit the United States on the Visa Waiver Program.