Hi,
I am credentialed in California. I think that you would need
a California teaching credential. Sometimes, American states
will recognize the teaching credentials earned in other
American states but I don't think foreign credentials are
recognized.
You should look at the California Department of Education
website. The answers should be there. Or email the CDE with
your questions. Although, in my experience, they do not ever
reply. You will have better luck trying to call them but
again hard to get them to answer the phone.
There is an oversupply of elementary teachers in the states.
300 applicants for a single opening is not uncommon. But
there is a shortage of secondary math and science teachers,
if you were credentialed in these then I think you would
have an easy time getting a job here.
But all of these regulations are just for teaching in the
public schools. If you teach at a private school then you do
not need any kind of credential. However, be advised,
private schools pay about half or two-thirds the pay of a
public school and your benefits (medical, dental) will be
poor or non-existant at a private school. But on the other
hand, the private schools will be eager to hire you because
your English accent will give them an air of class that they
will love. Private schools are the height of pretentiousness
and depend on an illusion of elitism.