Askari can kind of be both "police officer(s)" or "soldier(s)". I think there's a bit of a Kenya/Tanzania difference and probably also a lot of regional differences as to which whether it's commonly used and with which meaning. If you want to be unambiguous:
polisi = police officer (plural polisi)
mwanajeshi = soldier (plural wanajeshi)
Those terms are helpful because they give clarity. In Tz, "Askari" is commonly used to refer to guards, though "Mlinzi" is also a guard. I guess askari is general, and the other 3 terms are more specific?
90% of the time Marekani is translated USA and in this sentence it is: American, and so I got is wrong.